As the political parties gear up for the next general election, Labour's troops have been warned they face a "tough fight" for re-election.

Tony Blair said his party should not take the result for granted as to do so would be "the surest way to suffer an electoral setback".

The next election is widely expected to be called for May 5 this year.

But the prime minister cautioned: "If I don't know the date of the election then no-one else does."

Blair said the election would focus on "whether on the basis of the economic stability that's been provided, the huge investment in public services and in the mechanisms of law and order, we can then continue with the process of change and reform so that we have a country in which there is opportunity not just for a few but for all".

"We are providing basic security for people and doing both within the context of a changing world," he said.

Blair also warned his party to prepare for a major battle to retain power.

War chests

His comments came as the FT reported that the Conservatives have already built up two thirds of their expected election war chest.

Party treasurer Jonathan Marland told the paper he had received or been promised at least £17 million of the £25 million the party is allowed to spend in the run up to the next election.

And Labour officials are also said to be expecting a series of big private donations to fund their campaign.

"This election, when it comes, has not been won yet," Blair told the BBC. "It will be a tough, tough fight for us. This is going to be a hard, tough election."

He added that the Conservative strategy was to say "we're not looking for an election win, we're looking just to reduce the majority".

Blair said that was "a strategy designed to get the Conservatives back in by the back door".

Brown bid

The prime minister was also forced to repeat denials of a rift between himself and Gordon Brown.

Blair said the chancellor would have a "central" role in the election campaign, despite reports that he had been angered by Alan Milburn's return to the Cabinet as election co-ordinator.

"We haven't decided exactly how the election will be run but I have no doubt at all it will be of the same strength and purpose and energy as his last contributions, [which] were of course immensely important," he said.

But Gordon Brown was on Wednesday setting out his own "alternative manifesto" for Labour.

"In this decade what can best illustrate New Labour's ambition for a Britain of aspiration and achievement is a manifesto that, instead of the previous lottery of children's services and the patchwork of childcare, could make it our priority that not just some, but all British children have the best start in life," the chancellor wrote in the Guardian.

"The popular demand for new children's services demonstrates decisively the irrelevance of those market fundamentalists who do not want to mend the welfare state, but end it.

"The challenge of modernisation is a government on parents' side to ensure they can both make effective choices to balance work and family life and have an effective voice in shaping the new provision."

While Brown was setting out his own vision for the rest of this decade, the prime minister was denying that he would lose influence the day after the next general election.

Blair has said he will serve a full third term, but would step down towards the end of the parliament.

"I have to say that in the year before I said it I had probably actually more speculation than since I've said it," he told the BBC.