The big four accounting firms defended their independence to a parliamentary inquiry on Friday, denying collusion and emphasising their value for money.
Labor MP Julian Hill asked representatives of KPMG, Deloitte, EY and PriceWaterhouseCoopers how often their chief executives had dinner together and if they discussed commercially sensitive information.
The committee heard the CEOs had associated socially and the question was taken on notice about how often this occurred.
The ballooning number of consulting contracts in the public service was the focus of the inquiry, with the big four winning more than $1.7 billion in government work over the past five years, with total federal government procurement worth more than $47 billion in 2016-17 alone.
Labor MP Julian Hill, who is deputy chair of the audit committee inquiring into government contracting, asked representatives of the firms if they had heard the government referred to as "the dairy".
"It's a term that I was told by a couple of people is unkindly used for the Commonwealth, because you milk it for all it's worth," Mr Hill said.
The senior partners present said their work was value for money and conflicts of interest were managed through internal processes.
Mr Hill asked the consulting firms if they had seen tenders for work that didn't need to be done, and was told at times requests came where it was evident to the consultants similar work had been done recently within the same department, but those within the department didn't seem to be aware the work was done.
"There's that communication issue that pops up sometimes," one representative told the committee.
The inquiry heard the levels of complexity involved in government contracting, with the major firms present explaining they sometimes have more than one Australian Business Number, leading to them sometimes being incorrectly classed as a small-to-medium enterprise on Austender.
Technology consulting company Accenture's head of health and public service Catherine Garner told the committee on some government projects, 90 per cent of those working on an Accenture project were sub-contracted again to bring in the expertise needed.
Deloitte partner Robert Hilliard told the committee the definition of consulting used by government was "quite dated" with most representatives supporting a move to make government spending on contracting more transparent.
Last week Labor committed to reduce the number of consultants working on public sector projects.