Tony Blair has rejected criticism from Tory leader David Cameron that he is "indulging in vanity" by staying on as prime minister until the end of June.
Mr Blair was accused of behaving 'like a pop star'
Mr Cameron said the PM was acting "like a pop star" by making several trips around the world.
Gordon Brown should take office now, rather than "wandering around the country with nothing to do", he added.
But Mr Blair said the Tory leader was "flailing around a bit", adding: "It's a little bit pathetic."
Mr Blair insisted important work was being carried out not just by him but by ministers acting "as a government".
He said this included international duties, such as the upcoming G8 summit in early June.
But Mr Cameron said: "There are urgent problems in our country, like the crisis in the NHS, that need to be sorted out now.
"Instead we have to put up with the farce of Labour's 'non-election campaign', with Gordon Brown wandering round the country with nothing to do and Tony Blair wandering around the world doing nothing but indulging his vanity."
He added: "In this country, we don't do 'farewell tours'. Tony Blair was elected to be the prime minister of this country, not a pop star."
Mr Brown will replace Mr Blair as Labour leader and prime minister from 27 June, after he was nominated for the role by 313 Labour MPs.
This made it mathematically impossible for his only rival - left-winger John McDonnell - to secure enough support to go to a nationwide ballot of Labour members, trade unionists, MPs and MEPs.
Mr Blair said: "There is a massive amount we are still doing. These are things I am right in the middle of...and I did not choose the date in an arbitrary way.
"This is politics and even on 26 June he [Mr Cameron] will be saying 'he should be going today'. That's just the way it is."