Former Liberal minister Bruce Billson has admitted to receiving an undeclared payment from a "friend" through his personal consultancy business while still a member of parliament.

The payment was in addition to a $75,000 annual salary from the Franchise Council of Australia (FCA) that 7.30 revealed last year was paid to Mr Billson while he was still an MP.

A parliamentary inquiry into Mr Billson's failure to list the FCA salary on the compulsory register of members' interests handed down its final report on Monday, recommending that the former member for Dunkley be censured.

It stopped short of finding that Mr Billson's conduct amounted to a contempt of parliament, which can lead to potential penalties of six months in prison or a $5,000 fine.

Billson received payment for 'adviser services'

But in a surprising development, the report revealed Mr Billson also failed to disclose another payment which he received while still in parliament.

"Mr Billson also stated in his submissions that he had received payment for the provision of 'adviser services' through Agile Advisory Pty Ltd, of which he was the founder and sole director," the report found.

The then-minister for small business notified the register of interests in 2015 that he had become a director of Agile Advisory, the trading entity of the Billson Family Trust, yet he never declared any income from the company.

Bruce Billson revealed he received payment for "adviser services" which he hadn't declared. ( ABC News: Nick Haggarty )

"As disclosed in the 7 March 2015 update to my statement of members' interest, Agile Advisory P/L had been activated as the trading entity of the Billson Family Trust," he wrote in submission to the inquiry.

"At that time I had begun advising a personal friend as a client as part of the activation of Agile Advisory and transition to a post-political private sector career."

Mr Billson did not say when he received payment from the friend.

"I had received payment for the provision of these adviser services. I acknowledge that a further timely disclosure of this to the register was required before the parliament was dissolved.

"However, due to an oversight, this disclosure was not made."

The committee found the failure to disclosure the Agile Advisory payment was not deliberate, and did not recommend any further investigation into the matter.

"The committee accepts Mr Billson's comments that he failed to comply due to error and oversight, as evidence that he did not intend to interfere improperly with the free exercise of the authority or functions of the House," the report said.

Mr Billson did not respond to the ABC's interview request and did not answer emailed questions.

"The FCA and I have demonstrated that during the weeks when my widely publicised appointment as a director and executive chair overlapped with the end of my term as a MP, there was no improper influence, advocacy, lobbying, conflict of interest or impact on the free performance of my parliamentary duties, and welcome the committee's conclusion 'that no finding of contempt could be made'," he said in a statement sent by text message.

Inquiry recommends censure

Bruce Billson left parliament after being dumped from the frontbench in 2015. ( ABC News: Matthew Roberts )

Mr Billson was the minister for small business when he activated Agile Advisory in 2015.

He was dumped from the frontbench when Malcolm Turnbull took the leadership in September 2015, and announced in November 2015 that he planned to retire at the following year's election.

He has previously apologised for failing to disclose his FCA salary, and has denied intentionally concealing the payments.

"My attention to my post-political transition should not have resulted in a diminished adherence to complying with the timely notification requirements of the Registration of Members' interests," Mr Billson wrote in a submission to the inquiry.

The parliamentary inquiry report recommended that Mr Billson be censured for "failing to discharge his obligations as a member to the house".

It also recommended that parliamentary rules to be changed to explicitly ban MPs from being paid to act on behalf of lobbyists.

The inquiry found the total payments to Mr Billson from the FCA amounted to $6,250.

Last year, Prime Minister Malcolm Turnbull ordered his department to investigate whether Mr Billson had breached ministerial standards.

That investigation cleared Mr Billson of any wrongdoing.

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