Labour is withholding campaign money from lazy MPs and candidates in marginal seats who are not showing an appetite to fight the election, The Times can reveal.

For the first time Labour election officials are demanding that those standing in marginal seats must provide evidence of the scale of their campaign before they are allocated funds for leaflets and mailshots.

This suggests that the party recognises that some candidates have effectively given up but is not attempting to replace them. This contrasts with the tightly disciplined marginal-seat campaign run by Lord Ashcroft for the Conservatives.

A Labour source said: “Are we really going to give money if we are not sure there is an active candidate or an active local party? No.” Some candidates have been told to double the number of “contacts” with voters — on the doorstep or by phone — in order to receive additional funding.

The revelation will add to the sense that momentum is draining from the party. Diplomats attending the Labour conference told The Times that they were writing communiqués describing how the party activists appeared unenthused or lacked the fire to stay in government. One expressed disappointment that many of the MPs that they wanted to see were not in Brighton. The party is very sensitive to accusations that fewer people are attending this year’s conference. It says that 220 of the party’s 300 MPs were expected to attend, although it is not clear whether they all turned up.

Large swaths of the hall were empty during the speech by Alan Johnson, the Home Secretary, yesterday.

Labour’s election team is concerned that some MPs do not realise the scale of the threat facing them at the next election. Some MPs in marginal seats, such as Gareth Thomas in Harrow West and Michael Foster in Hastings & Rye, are pounding the doorsteps at least three nights a week and one day each weekend to save their seats. “But I can’t claim that every constituency is working as hard as it could,” a source said.

They suggested that some candidates with bigger majorities — likely to be over 9,000 — do not realise that they are vulnerable and are failing to put in the preparatory work to shore up their position.

They drew comparisons with the Scottish parliamentary elections in 2007, when some Labour constituencies with smaller majorities were saved from the SNP by a dedicated ground campaign, but MSPs with bigger majorities were toppled.

Labour claims that it has a far more advanced computerised system than the Tory equivalent because it contains more than 15 years’ worth of canvass returns as well as detailed information on preferences provided by credit agencies such as Experian.

In January Labour employed two pollsters from the Obama campaign, Joel Benenson and Paul Tewes, who masterminded the breakthrough victory in the Iowa caucuses last year. “What impressed us was their humility — they acknowledged that they were part of a team rather than the winning force within it,” said a source.

Activists have received a campaign timetable pointing to a general election on May 6. A Labour document distributed at the conference sets out a day-by-day schedule for building support, suggesting a four-week election campaign starting in April. The handbook gives activists tasks to perform every day, granting them 17 days off between October 1 and March 31. On Thursday, March 18, it instructs them to “follow up Budget coverage”.

The party is relying on union muscle to boost its vote. Strategists say that one of the lessons from the US campaign in 2004 is that union members are more likely to be persuaded to support a candidate by their colleagues than by someone in a call centre. Unite, under the direction of the political officer Charlie Whelan, has led the way on this but other Labour-affiliated unions have been slower to pick up the challenge.

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