Brown's challenge to battered Blair: Name the day

Unprecedented attack by Chancellor, calling on PM to 'set down' timetable for exit. Secret letter leaked to 'IoS' reveals plan by rebel Labour MPs to 'ambush' leader

Gordon Brown will today urge Tony Blair to stand aside as Prime Minister, challenging his embattled rival to "set down" a clear timetable for a handover of power.

In a carefully timed intervention, Mr Brown will tell Mr Blair that he cannot ignore the "warning signal" from voters at last week's local elections, saying that Labour must "do what we have got to do". He will tell Mr Blair that "there is going to be a transition to a new leader" and that "the important thing is that we set down how we are going to bring about that".

Allies of Gordon Brown yesterday stepped up calls for Mr Blair to name a date, as backbench Labour MPs prepared to sign a letter calling on him to set out "a clear timetable" for succession. The letter, obtained by The Independent on Sunday, is expected to gain the backing of up to 50 Labour MPs. Rebels said yesterday that they wanted Mr Blair to tell MPs, by the summer, when he will go.

Mr Brown's remarks, in a GMTV interview broadcast today,were foreshadowed yesterday by supporters, including Andrew Smith, the former Cabinet minister, who called on the Prime Minister to name the day he will leave Downing Street.

Mr Brown's intervention will be interpreted at Westminster as a direct challenge to Mr Blair. Issuing a clear call to the Prime Minister to name his departure date, Mr Brown will also say that the Labour Party now has to "do what we have got to do... to deal with those challenges ahead".

Mr Smith, a close ally of the Chancellor, warns that the party faces " destructive instability".

Writing in today's IoS, Mr Smith says Tony Blair must name the day of departure or risk further damaging the party and the country. "I think it would be better, not just for the country and the party, but also for the Prime Minister himself, if he made clear what the timetable is, and the sooner the better," he writes.

Another senior ally of the Chancellor warned that the PM would face intolerable pressure unless he acts. "If he doesn't listen, pressure will just get bigger and bigger. Bunkering down will be a bad mistake," he said.

Labour MPs from all wings of the party fear that Labour will be torn apart if Mr Blair insists on serving a full third term. They warn of civil war unless he sets a timetable for leaving Downing Street.

The letter asks Labour's ruling body, the NEC, to work with Mr Blair to "lay out no later than the end of the current parliamentary term a clear timetable and procedure for the election of a new Labour Party leader".

Tomorrow, Labour MPs plan to break their silence about the need for a smooth transition at a meeting of the parliamentary party in Westminster at which they will assess the results of the local elections. Several MPs indicated that they will use the meeting as a forum for calling on Mr Blair to set a date for leaving office.

On Friday evening, Mr Brown and Mr Blair held a face-to-face meeting at Downing Street to discuss "the renewal" of the party following the election results.

In a further worrying development for Mr Blair, Jane Kennedy, the Health minister sacked on Friday, is expected to round on the Government's NHS reforms. Geoff Hoon, however, has decided to accept his demotion after a weekend "wobble", say friends.

No 10 indicated that Mr Blair will try to regain the initiative, following his reshuffle, with a press conference and letters to new ministers setting out his demands for delivery in office.

But ministers warned that MPs could rally against the Prime Minister during a vote on education later this month.