This time last year at the Labour Party Conference, Gordon Brown was walking on water.

He had had a triumphant three months as Prime Minister after an agonising wait of 10, if not 13, years. The young pretender was finally gone; the legitimate heir was at last in the saddle. Labour was to regain its soul and march to the sunny uplands of a fourth term.

This week that dream has turned to dust. The Ipsos-Mori poll showed Conservatives above 50 per cent and Labour crucially slipping below 25 per cent. The YouGov poll confirms this slippage. This is a turnaround of 30 percentage points since last year. Yesterday's poll in The Observer projects only 160 MPs, worse than in 1983 and only a bit better than 1931 when another Scottish leader of the Labour Party made a mess of fighting a global crisis, divided his Cabinet and split the Party. Are we back to the Ramsay MacDonald nightmare? It took 14 years then before Labour got back into power.

Brown's slide began soon after last year's conference. The hurried trip to Iraq to steal Cameron's thunder, the false trail laid about a likely election, the copycat cut in inheritance tax, were signs of a loss of nerve. Northern Rock went under and no solution was in sight. Then followed the 10p fiasco and Brown lost the one strength he had — as a guardian of the nation's finances and a protector of Labour's core values.

It was in the wake of this in April that I took up my role as a canary in the coal mine. In an interview with the Standard, I warned that Brown was failing to communicate; he had the talk to be a good PM but not the walk. I was asked afterwards — by a number of channels to the PM — to send a memo setting out my case. I did so but did not get an acknowledgement from No 10. Advice seems to fall on deaf ears anyway.

As I had warned, we lost the local authority elections, the London mayoral election and then Crewe and Nantwich. The final hammer blow was Glasgow East, Labour's 25th safest seat. There has been no improvement during the summer and here we are with a 25 per cent-plus Tory lead.
Some MPs and ministers say Brown is the only one who can steer the British economy through a crisis. But examine his economic expertise. He promised to eliminate boom and bust but according to the IMF, the UK is the one economy most likely to face recession, with unemployment rising to two million by the year's end.

The Golden Rule was fudged and fudged again until Alistair Darling inherited an empty kitty. Brown talked of prudence but the Public Private Partnerships have saddled us with a lot of debt off the balance sheets. Those chickens will come home to roost; perhaps Brown sensed he would not be in charge when they did so.

He divided up the oversight between the Bank of England, the Treasury and the FSA. The result was that the crisis at Northern Rock took ages to sort out. Now the US has shown the way, so the Lloyds Bank takeover of HBOS was swift and timely. The solution to the 10p tax rate should have been a simple lump sum of £150 to the five million who had lost out. I had proposed this in my memo and also publicly. But Brown forced Darling to make a much more expensive settlement — £120 to 23 million taxpayers — costing £2.7 billion, with the majority of beneficiaries being the better off, to buy the Crewe by-election. In vain.

But even more worrisome to Labour MPs should be the way the Lib-Dems' Vince Cable has proved that sound economic thinking can be combined with a light touch — a politically winning combination. While Brown has once again repeated his well-worn clichés about tough long- term decision-making, Cable's new tax-cut proposals show that good economic decisions are not necessarily “tough”; they have to be clever and politically attractive.

A lesson in history presents itself which Labour would do well to recall. The Liberals won a landslide victory in 1905, headed a radical reformist government which founded the Welfare State, reformed the House of Lords and passed the Irish Home Rule Bill. After 10 years, the then Prime Minister Herbert Asquith was shunted aside by a man who had been his Chancellor of the Exchequer, David Lloyd George. It split the party, and while Lloyd George governed for six more years with Tory support, the Liberals went into the wilderness and have not been in power since 1922. Is that what the polls tell us is Labour's future?

There is a way out. This is for Brown to see the writing on the wall and declare that he will step down once the Labour Party has chosen someone else. It cannot be pleasant but the choice for him is to stick around in office and lose 300 seats at the next election, sending the Labour Party into exile for decades, or to take a chance that someone else would be better leading the party. A vacancy could trigger a leadership election now and a new leader could be ready to take over by the New Year.

There are many likely candidates. But the lead contender is obvious. David Miliband has already shown maturity in not contesting last year and setting out his vision during the summer. I have known David as an ideas man since John Smith's days, when he was secretary of the Commission on Social Justice. He has experience of generating ideas from his time in No 10 — and of implementing them as a minister. He was a brilliant cabinet minister at Defra and now at the Foreign Office.

Miliband has vision, youth and already a long stint in policy making behind him. He is what we need for the Home Counties, where the battle will be won or lost.

At the first PLP meeting after the 2005 victory, Tony Blair was asked to declare his timetable for an orderly transition of leadership. By the following September there was a revolt by 10 junior ministers orchestrated by we-know-who and Blair was forced to declare his hand. Last September Brown got what he had plotted for. But he has failed. So at this conference delegates have the right to ask Brown for an orderly transition for the sake of the party he loves so much.

If he does not, then someone ought to remind him of Cromwell's words to the Long Parliament. You have been here too long. In God's name — and for Labour's sake — go.

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