Read Charles Clarke's doomsday memo in full

A former cabinet minister has circulated a “doomsday list” of Labour MPs at risk of losing their seats if fewer than 7,500 voters switch sides.

Charles Clarke, the former home secretary, warns that because of boundary changes the party needs to lose only 24 seats, predominantly in London and the southeast, to be stripped of its overall majority.

This will happen if just 7,417 people in the 24 seats who voted Labour at the last election vote next time for the party that came second.

Clarke points out that a disproportionate number of these marginals are in north Kent and Essex, prompting MPs to dub the next election the Battle for Bluewater after the giant shopping centre near Dartford.

In most of the seats, the Tory party is the main challenger.

The dossier, which has been e-mailed to selected MPs, is adding to nervousness in the already jittery parliamentary Labour party. One who received the document last week said: “It shows just how close we are to annihilation. If we lose our overall majority, it is unlikely the Lib Dems will keep us in power. Gordon needs to connect with voters, particularly in these crucial seats in the south.”

Brown has an overall majority of 67. However, the abolition of six Labour-held seats and other boundary changes favouring the Conservatives mean that he will go into the next election defending a notional majority of just 47.

A Sunday Times poll last week put Labour on 27%, 16 points behind the Conservatives on 43% – a 10% swing to the Tories since the last general election. However, Clarke points out that it would take a swing of less than 2% to wipe out Labour’s majority.

In the introduction to his four-page dossier, Clarke states: “Labour holds 27 seats with a majority of less than 3% over its main opponent . . . which would change hands with a universal 1.5% swing.”

The MPs on the doomsday list include several members of the government, including Bill Rammell, the universities minister; Jim Knight, the schools minister; and Phil Hope, the Cabinet Office minister.

A string of ministerial aides, including Angela Smith, Brown’s parliamentary private secretary, are also at risk of losing their seats. Clarke, who in the past has been an outspoken critic of Brown, declined to comment yesterday on the prime minister’s predicament.

But he said: “I prepared this document to understand the nature of the political battleground. The message that it sends out is that Labour has to make a clear case to win seats in London and the southeast.” Michael Thrasher, professor of politics at Plymouth University, agreed that a small number of votes could determine the outcome of the next election. “The reality is that a very small swing indeed of less than 2% would deprive Labour its overall majority. On the new boundaries, the electoral battleground will be centred around just 24 seats.”

Times Recommends

• Model judge and his funky new gown
• First review: Sex and the City
• Thatchers clutch at straws after crops fail