Peter Hain has received a vote of "utmost confidence" from his constituency party amid the donations row over his deputy leadership bid.
Donations to Mr Hain's deputy leadership bid are under scrutiny
Neath Constituency Labour Party praised the work and pensions secretary for having the "highest integrity".
It comes as the Electoral Commission is looking into late declarations of £103,000 in donations to Mr Hain.
Clive Phillips, of Neath Labour Party, said Mr Hain, who is also Welsh secretary, was an "outstanding" MP.
He spoke out after Prime Minister Gordon Brown had earlier conceded that Mr Hain was guilty of "an incompetence" over the donations to his failed 2007 Labour deputy leadership campaign.
The prime minister told ITN Mr Hain had made a mistake he had "readily admitted to" but there had been "no corruption".
Mr Hain, who came fifth in the six-candidate Labour deputy contest, is also facing a separate inquiry by Parliamentary Standards Commissioner John Lyon.
Mr Hain said he had been "open and clear" and would co-operate with any inquiry. It has emerged that on Tuesday he apologised to cabinet colleagues for the row.
Downing Street acknowledged that the uproar over the £103,000 had become "an issue", and that was "why he said sorry".
At Wednesday's two-hour meeting of the executive committee of Neath Constituency Labour Party, Mr Hain was given unanimous backing.
Mr Phillips said Mr Hain had always displayed "the highest integrity and honesty" since becoming Neath MP in 1991.
"We have utmost confidence that Peter's account and apology for administrative failings in his campaign office will be accepted," said Mr Phillips.
"We expect the ongoing investigations will lead to a satisfactory outcome and he will be able to continue serving the country with the same commitment and distinction that he has shown in the past."
Mr Phillips said the MP had "an exemplary record of public service in government, primarily as an outstanding secretary of state for Wales since 2002".
He had also dealt successfully with the "challenging portfolios" as Northern Ireland secretary and in work and pensions.
Earlier, Mr Hain faced taunts of "incompetence" from the Tories as he took to the dispatch box for his first scheduled Commons questions sessions since the row over the donations emerged.
Conservative shadow work and pensions secretary Chris Grayling claimed it "all appears to be getting a bit much" for Mr Hain.
During a debate on pensioner poverty, Mr Grayling pressed him: "Can you now tell us why you believe you are still the right man to do the job?"