The claim came as fresh questions arose as to how the snack-food giant Cadbury came to receive a $16 million pledge from the Coalition in the lead-up to the 2013 election.

Senator Nash's chief of staff Alastair Furnival resigned this month when it was revealed by Fairfax Media that he had retained ownership of a lobbying company in breach of the ministerial staff code of conduct. It followed a decision by the Minister's office to take down a healthy food website seen as hostile to the snack food industry.

Mr Furnival had worked for Cadbury and months earlier had lobbied the Tasmanian government on behalf of the company to secure $400,000 for a visitor centre.

Pictures located by the Seven Network show Mr Furnival was at the Cadbury announcement in August sitting with Mr Abbott and other senior figures. The pictures suggest Mr Furnival, who went on to hold a key post in the Abbott government with critical responsibility for food policy, was central to Coalition discussions resulting in a promised transfer of taxpayer funds to the company.

Mr Abbott announced the $16 million pledge during the election campaign. He has since pointedly refused to say what links he had to Mr Furnival and what role Mr Furnival might have played in brokering the proposed transfer of millions in taxpayer funds to the multi-national owned company.

Also sitting with the pair was Liberal Senate leader Eric Abetz and party veteran Philip Ruddock.

On Tuesday, Mr Abbott told Parliament Mr Furnival had resigned a fortnight ago because he had been ''dilatory'' in his requirement to divest himself of shares in the company. The different explanations prompted the opposition to ask Mr Abbott which of the two ministers had misled Parliament.

Abbott said both he and his Minister were correct, while Senator Nash also declared she had done nothing wrong despite the Prime Minister's office advising that it was the responsibility of ministers to ensure there was no conflict of interest among their staff.

Her assertion also appeared at odds with her previous statement to the Senate on February 11 that her then chief of staff had no links ''whatsoever'' to the firm Australian Public Affairs.

In a fiery session of Senate estimates, the embattled Minister revealed she had known Mr Furnival for years and was well aware of his ownership stake in the lobbying firm and links to the snack food industry.

APA had undertaken significant lobbying work on behalf of Cadbury.The opposition demanded to know what had led to Mr Furnival's employment by the Abbott government, and what discussions had taken place between Senator Nash's office and that of the Prime Minister.

''I am not commenting on any discussions I had with the Prime Minister or the Prime Minister's office,'' she said. While the Minister refused to answer questions about whether she was asked to resign, Mr Abbott eventually said ''I've had no such conversation with her''.