The former member for Waimakariri, who is now a list MP, appeared on TV3's The Nation to answer questions about $17,500 in campaign donations from Independent Fisheries Ltd (IFL), which owns land in western Christchurch.
Mr Cosgrove introduced a private member's bill in July 2009 that would have helped pave the way for the development of land in the area, including some belonging to IFL, by protecting Christchurch Airport from noise complaints.
Electoral Commission returns filed by Mr Cosgrove show IFL, which had previously given money to his campaign and that of National's Christchurch Central candidate Nicky Wagner, made a $2500 donation to him a few months later.
The firm gave a further $15,000 to Mr Cosgrove's campaign in June last year.
In August, with new sections suitable for rebuilding in Christchurch in short supply because of earthquakes, Mr Cosgrove called on the Government to pick up his legislation.
On Saturday, the MP told The Nation that if the allegation was that he took a donation from a company to draft legislation, that was not true.
Yesterday, he told the Herald he "openly, honestly and transparently declared, as the law requires, those donations" and had never accepted any money if it came with preconditions.
There was no conflict of interest around the donations and his bill, "because I declared everything".
He had briefed Labour leader David Shearer and deputy leader Grant Robertson on the matter.
Mr Robertson yesterday confirmed Mr Cosgrove had spoken to him about the matter and said there was no question that the list MP would be stood down from his duties as state-owned enterprises, commerce and associate finance spokesman.
"He's declared the donations, he's been completely upfront about what's happened, that's good."
In a statement to The Nation, Independent Fisheries director Mike Dormer said Mr Cosgrove's bill "was not initiated by IFL, or at our request. IFL did not make any payments to him in connection with this legislation."
