David Miliband is among a host of Cabinet members who has pledged their backing for Gordon Brown - but he also suggested the Prime Minister had failed to perform up to now.
The Foreign Secretary said Mr Brown was displaying "more vigour and determination" than before and would "prove people wrong" by winning the next general election.
He was joined by Health Secretary Alan Johnson, who described Mr Brown as a man "who has good experience, who has intelligence and an absolute remorseless focus", and by Justice Secretary Jack Straw who insisted the Prime Minister was "secure".
The trio's comments came after an awayday for ministers in the West Midlands - which included the first Cabinet meeting held outside London or the Prime Minister's official country residence Chequers in nearly a century.
Mr Miliband said: "I think Gordon is leading us with more vigour and determination and will prove people wrong. I am absolutely convinced that Gordon can lead us to victory. He has enormous values, drive and vision and I think we are going to prove people wrong."
Despite the overt support the comments may cause some dismay in Downing Street as Mr Miliband was at the centre of fevered speculation over a leadership challenge last month.
However, Mr Johnson said: "I don't think David Miliband said anything but positive words about Gordon's leadership. When you see the problems that we are facing, that the country and the world are facing, the plan of action taken in America yesterday, the discussion we had with people in Birmingham was about how do you get through these difficult times."
Saying the premier was "secure", Mr Straw added: "This Prime Minister is exactly the same person today as he was 15 months ago, when he was elected not by acclamation by the Labour Party, but because virtually everybody in the party wanted him to do that job."
During the day Mr Brown issued a rallying cry to ministers insisting he would draw on personal trials such as losing his eye in guiding the country through the current economic turmoil.
And the Prime Minister said the UK could be a "great success story" of the 21st century.