Tony Blair's aides have moved to dismiss talk of him being a spent force and a liability.
Mr Blair is to address Labour party activists in London
He is due to stand down this year but one senior aide said he will be working "flat out" until he announces the day.
Mr Blair has come under pressure to go now after being interviewed as a witness for a second time by police investigating cash-for-honours claims.
Later, he is expected to tell activists Labour will only win a fourth straight election with the right policies.
Mr Blair will appeal to the party to take forward his reform programme and say the next general election will not be decided by "controversy that passes".
Senior Labour figures, including party chairman Hazel Blears and former leader Neil Kinnock, have said the cash-for-honours inquiry is damaging the government.
Some critics within Labour are concerned there may be a poor showing in local elections in May.
Conservative leader David Cameron has called on Mr Blair to stand down now "in the national interest" while Liberal Democrat leader Sir Menzies Campbell has said the PM should go "sooner rather than later".
But Mr Blair's senior aides insist his energy and ambition are undimmed.
Asked if the PM feels weary one said: "He's going to be working flat out until the day he decides to announce he is standing down. I have no doubt."
Mr Blair himself told BBC Radio 4's Today programme he will not give in to pressure to quit over the cash-for-honours affair.
He said he intended to "get on with the job".
Addressing Labour's National Policy Forum in London later, he will say: "The fourth election will not be decided by current events.
"It will be about whether we have the dynamism, energy, vision and, above all, clear, well-thought-out policies for Britain's future."
The prime minister will also highlight pending government business.
"In the coming weeks, issues like welfare reform, the next stages for the development of our universities, offender management and reform of the Home Office, climate change ... not to mention decisions like Trident, will be driven forward," he will say.