The two leaders have clashed numerous times

"Everyone knows I'm going next week, they want to know when he is going," said Mr Howard, asking if he still planned to serve a full third term.

The prime minister has said he will leave No 10 before the next election but refused to be more precise.

Mr Blair said their new leader would be unlikely to improve Tory fortunes.

Mandelson joke

Mr Howard is due to hand over to either David Cameron or David Davis once the results of their Tory leadership run-off are declared next Tuesday.

He said Mr Blair had left a legacy of higher taxes, higher borrowing, lower savings, lower crime clear up rates and blocked reform in public services.

Michael Howard's farewell PMQs point-by-point

And in his last prime minister's question, Mr Howard recalled Mr Blair famously saying: "My project will be complete when the Labour Party learns to love Peter Mandelson."

"Can he give us a progress report on that," he asked, to cheers and laughter from Tory MPs.

Mr Blair admitted: "Well, I may have to say on that one: a lot done, a lot left to do."

The biggest test for a political leader was putting its policies to the British public, he said.