Gordon Brown fighting for his life

Peter Mandelson has urged Labour MPs to stick with their leader, asking them not to join the 'cyber-plot' against Gordon Brown – an unsigned email letter doing the round of Westminster, calling on the Prime Minister to resign.

But Mandy admits that backbenchers are in a "grumbly mood"  - possibly the greatest understatement of the year so far. More appropriate words might be "rebellious and panicky".

Labour is bracing itself for a serious drubbing in today's local council and European parliament elections which will see polls in 27 English county councils and seven unitary councils, and for 72 Euro MPs. Results will start coming in on Friday and Sunday night respectively.

Brown's backbenchers fear the outcome will see unprecedented losses that will set them on course for inevitable defeat in the general election in a year's time. Meanwhile the sheer chaos sparked by the expenses crisis and panic over poll ratings has led to claims the Government is disintegrating before our eyes.

The pre-emptive resignation of ministers, headed by Home Secretary Jacqui Smith and a hugely fed-up Communities Secretary Hazel Blears, has added to the sense that the time is up for Gordon Brown.

There was, and still is, however, no clear well-coordinated single plot to get rid of Brown - even though there is an increasing expectation in Westminster that he might not make it through the next few days.

What there does seem to be is a series of unrelated challenges popping up left, right and centre and which, combined, are seriously undermining Brown's authority. Against all this, Lord Mandelson's plea sounds like whistling in the wind.

The email 'cyber-plot' is the closest thing to an organised coup and is widely believed to be being organised by the same people who have been at it before. Labour whips believe former Blairitie ministers Charles Clarke, Alan Milburn and Stephen Byers are behind it - and they are probably right. But for the plot to succeed, it would need wider support, and the plotters clearly believe they will get that.

The letter, short and sweet, reads: "Over the last 12 years in Government, and before, you have made an enormous contribution to this country and to the Labour Party and this is very widely acknowledged. However, we are writing now because we believe that in the current political circumstances you can best serve the interests of the Labour Party by stepping down as Prime Minister and so allowing the party to choose a new leader to take us into the next General Election."

The aim is to get the 70 signatures needed to force a leadership election or, failing that, enough signatures, 40 or 50, to so undermine the PM that senior Cabinet members will decide to pull the rug from under him.

But even before Brown gets to that possible crisis, there is his reshuffle, intended to re-assert his authority and give the Government new impetus. Two of those marked for the sack have already gone and it has now emerged that Chancellor Alistair Darling and Foreign Secretary David Miliband have signalled they would rather leave the Cabinet than be moved - a direct challenge to Brown's authority. It may be that Brown simply cannot carry out a major reshuffle – which would only weaken him further.

There is still the possibility that a senior figure, maybe even Hazel Blears, could deliver a speech so critical of Brown that it prompts others to move against him, even put up a stalking horse candidate against him. Charles Clarke's name has been mentioned in this context before.

So what tricks does the Prime Minister have left up his sleeve? Not many. He can simply refuse to budge and it is hugely difficult for MPs or even Cabinet ministers to then get rid of him short of mass front-bench resignations.

And he still has that reshuffle which he could use to promote his enemies in an attempt to stop the plots - although former Home Secretary John Reid is said to have turned down a return to Cabinet (an offer Downing Street denies). ·