Former ministers - and the organisations that hire them - should have their access to Parliament House revoked if they are found to breach the lobbying code of conduct, a Senate inquiry has been told.
As former Coalition ministers Julie Bishop and Christopher Pyne fend off accusations their post-politics jobs are in breach of the 18-month cooling off period, the Grattan Institute has described the current rules as "unenforceable".
The prime minister has the discretion to determine if a breach has been committed, and there are no practical sanctions if a former minister is found to be lobbying on an issue in their portfolio 18 months after leaving parliament.
The think tank says the remit of Independent Parliamentary Expenses Authority should be extended to investigate possible breaches of the code of conduct, publish findings and refer non-compliance on.
A separate ethics adviser should also be appointed, to allow current and former parliamentarians to seek advice when they are not sure if they are in breach of the rules.
If the former minister is found to have breached the code, their political party should pressure them to resign from their new job or delay their start date.
If they refuse, their access to Parliament House and government officials should be restricted.
"For example, if the individual has a parliamentary pass it should be taken away until they resign or their 18-month ban is up," the institute said.
The ex-minister should also be barred from political parties, with fines for parties that don't ostracise the offending member.
The former minister's new employer should be restricted from applying for government tenders, and their access to Parliament House should be revoked.
"Generally, penalties related to access are preferable over fines because fines can be absorbed by some employers simply as 'the cost of doing business'," the institute said.
"In contrast, access is critical to influence, and this is at least partly what employers are 'buying' when hiring former ministers within the 18-month window."
Transparency International has called for the ministerial standards cooling-off period to be extended to between three and five years.
The group said the federal lobbyist register should publish data on who has an unrestricted Parliament House security pass to "identify commercial and in-house lobbyists with privileged behind-the scenes, significant and regular business access to politicians".
But outgoing Prime Minister and Cabinet secretary Dr Martin Parkinson said former ministers should be able to get a job post-politics.
"In terms of post-ministerial employment, I believe that a former-minister should have the ability to gain employment after they have left the parliament - whether or not that employment relates to the matters they dealt with as a minister," Dr Parkinson said.
"However, it is important that former ministers do not misuse the knowledge and information they have gained from their ministerial positions to benefit themselves or others."