Joel Fitzgibbon had been a fine minister, Australia's prime minister said
Australia's Defence Minister Joel Fitzgibbon has resigned.
He had been under fire for failing to declare gifts received, including two trips to China.
There had also been a conflict over contact between the government and his brother's company, Mr Fitzgibbon said in a statement.
He is the first person to leave the Labor government ministry since Prime Minister Kevin Rudd won power in November 2007.
Australian newspapers reported that Mr Fitzgibbon's letter to Mr Rudd said he could not be "satisfied" that he had "entirely conformed with your Ministerial Code of Conduct".
The prime minister told a press conference on the issue in the capital, Canberra, that Mr Fitzgibbon had been "a first class defence minister".
However, he added, his ministers knew that his government "expects high standards of accountability".
On Tuesday night, Mr Fitzgibbon had been forced to apologise to parliament for failing to declare accommodation expenses paid for by the private health insurance company headed by his brother, Mark.
He had also had to correct the public record in March this year when it emerged he had not paid for travel paid for by Chinese-Australian businesswoman Helen Liu.
Mr Rudd said a statement would be made "very soon" on a replacement defence minister.