But most people know little about the lobbying industry and the people filling its ranks.

Some in Parliament complain oversight and transparency of those who seek to influence are lacking.

The controversial issue has resurfaced, as a Senate inquiry into lobbyists and their access to Parliament House gets under way.

While several independent and Greens politicians have expressed concerns about the level of access lobbyists have to Parliament, it's not clear whether the major parties are interested in change.

The debate has raised questions about who counts as a lobbyist, and what role they play in the democratic process.

Broadly, a lobbyist is someone who seeks to influence government decision-making around particular causes.

Lobbying can include calling for legislation to be amended or a policy or program to be changed, or making a case to win a contract or grant, or receive funding.

The public is well aware of the role of powerful groups in lobbying for commercial interests, such as the Minerals Council, the Pharmacy Guild or the Property Council.

But Australia's definition of a lobbyist in practice is actually "too narrow", some experts, including Monash University Associate Professor Yee-Fui Ng, say.

"We're not getting a full picture of who is lobbying government because the definition of lobbying, or lobbyist, is too narrow," she said.

This comes down to the two frameworks that apply to federal government lobbyists.

The first is a register, managed by the Attorney-General's Department, which requires lobbyists to declare who they are and which clients they represent.

Only those who act on behalf of clients are listed on this register, excluding in-house lobbyists who work for an employer.

It means only about 20 per cent of lobbyists are covered, Associate Professor Ng says, and the department also exempts charities, religious organisations and not-for-profits from the register.

Another system exists in Canberra, where lobbyists are mainly distinguished by the orange lanyards and passes which give them access to the private areas of Parliament House.

Complicating things further though, the public servant in charge of handing out these passes says that they shouldn't be called "lobbyist passes" at all.

This is because those who wear them are engaged in areas beyond representing commercial interests, including advocacy groups, non-government organisations, peak bodies, academics, unions, local government and faith-based organisations.

Lobbying takes place both behind closed doors and very publicly.

Groups seeking to influence public perceptions and pressure the government can do so by launching advertising campaigns and engaging with the media through interviews and press conferences.

The mining industry launched a huge campaign against the Rudd government's Resource Super Profits Tax in 2010, spending about $22 million in the process. It tanked the tax and is thought to have contributed to Kevin Rudd's ousting.

More recently, the Pharmacy Guild lobbied hard to dissuade the Albanese government from introducing a 60-day dispensing policy.

The group eventually secured $3 billion in funding for the sector, in a deal which helped it to move forward with the plan to increase prescriptions for more than 300 common medicines from 30 days to 60 days.

But lobbyists influence decision-makers in more covert ways, which is where Parliament's orange passes factor in.

They have to be sponsored by an MP or senator to receive the pass, but once obtained, they have the power to wander the halls of power.

They can use these to attend scheduled meetings, to hold press conferences, and to form impromptu connections.

Independent senator David Pocock called for a Senate inquiry into lobbyists in December, citing a need for more transparency about how lobbyists gain access and what oversight there is.

He, and others, say they're concerned about lobbyists roaming free around Parliament, often door knocking on the offices of those in power and sometimes camping outside of them.

This followed independent MP Monique Ryan introducing her own private members' bill in the lower house, calling for sweeping changes to the system.

It's not the first time the issue has been raised - the Australian National Audit Office has conducted two inquiries into the management of the Lobbyist Code of Conduct in the past two years.

The second audit, released in 2020, was conducted after recommendations from the earlier inquiry in 2018 were not implemented.

Those who want reforms say there is a lot that could be done.

They want to see the Attorney-General's Department increase the scope of its Lobbyist Code of Conduct to include those who work in-house, like places such as Canada, the United States - and even NSW - already do.

There are also questions about whether sanctions for breaching the code are sufficient, and if they're being enforced.

There were 28 reported breaches of the code between 2021 and 2023, but only seven were found to be actual breaches. Of those, no one was struck from the register.

"Even the oversight of third-party lobbyists is weak, relying on individual public servants to take the initiative to report violations to the code of conduct," the Australia Institute researcher Vivien Clark told the Senate inquiry.

"The only listed sanction for violating the code of conduct is being deregistered."

There are also some calls for the code to be legislated - as it is in the United Kingdom, Ireland, Canada, the US and NSW - which could mean the introduction of a regulator and harsher penalties.

The Department of Parliamentary Services, which administers the so-called "lobbyist passes", could also play a significant role in increasing transparency.

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This could include publishing the names of those who hold passes, as well as the names of MPs and senators who sponsor them.

Right now, the department will not publish the list of those who hold these passes (1977 people as of March 31) because it says it would breach privacy laws, and could make them targets for foreign interference.

A simple fix could be requiring ministers to publish their diaries on a regular basis, as some other jurisdictions already do.

The sponsored pass system could also be scrapped for lobbyists - requiring them to be escorted in. But parliamentarians, especially backbenchers who are allotted fewer staff, say this would not be possible for logistical reasons.

The peak body representing government relations professionals says it is mostly comfortable with the existing system, but would support stricter scrutiny of who is eligible for passes and bolstered sanctions for those who act poorly.

In its submission to the inquiry, the Australian Professional Government Relations Association pushed back against naming those who hold sponsored passes.

This would duplicate information already presented on the lobbying register, "unreasonably target only one cohort of pass holders" and add to administrative burden.

Government relations firm, Hawker Britton, agrees that the current definition of lobbying is too narrow and that it should encompass in-house lobbyists.

It did not weigh in on whether details about pass holders should be published, saying this is ultimately a decision for Parliament, but its submission outlined that it is supportive of "more transparency, not less".

Other organisations, which represent civil society groups, say they want fairer access to sponsored passes, as documents to apply for these aren't made readily available, giving larger organisations an unfair advantage.

Former senior public servant John Menadue claims Australia is "stuck" on this issue because the pipeline of former politicians, staffers and officials into lobbying roles dissuades those in power from making changes.

"The problem is that those that benefit from lobbying, are not just the companies and organisations themselves, but politicians.

"In fact, many of them after public life become lobbyists."

There are rules for those transitioning from government roles to lobbying, but only for third-party lobbyists.

The Senate inquiry is not due to report back until the end of April, when it will become clear what representatives think should happen.

Any recommendations they do make will be considered, but don't have to be implemented.

In the first public hearing, Liberal and Labor politicians raised some concerns around the scope of reforms being floated.

Chair of the committee, Liberal senator Richard Colbeck, said he wanted to "dispel the misconception" about lobbyists in Parliament House.

"...It's not a free-for-all that exists within this building, it's an organised process," he said.

"And I just want to dispel the misconception that might be there, that there's people sticking their heads inside your door all day distracting you from your business."

Senator Pocock has contested this.

Labor senator Louise Pratt has also raised concerns about the broad group who hold orange passes, and whether naming them would unfairly target groups who are seeking to advocate for vulnerable Australians.