Anger over plans to close 2,500 post offices sparked a Labour revolt last night that saw the Government's Commons majority slashed in a crunch vote.

One leading backbench critic claimed as many as 20 colleagues had backed a Tory call for the suspension of the controversial programme and many others had abstained.

The Opposition motion was defeated by only 20 votes, meaning Prime Minister Gordon Brown's working majority of 67 was cut by more than two thirds.

In East Lancashire, 24 sub-post offices are earmarked for the axe which prompted an outcry from angry customers.

The Lancashire Telegraph has launched a campaign against the proposals.

Rebel MP John McDonnell said: "The Government has always underestimated the strength of anger on the Labour backbenches against the privatisation and cuts in this essential public service.

"The vote is a huge embarrassment to the Government and shows that a large number of Labour MPs are even prepared to support a Tory motion to demonstrate their concern.

"The Government is the sole shareholder in Royal Mail and could stop this closure programme in its tracks."

The Tories had urged the revolt, pointing out that 90 Labour MPs, including seven Cabinet ministers, had campaigned against proposed closures in their own constituencies.

Mr Brown had told the Commons he wanted to see good Post Office services in every part of the country but stressed the organisation was losing £500,000 a day.

At question time, he said the Tory motion did not propose extra money for the Post Office, adding: "Unfunded promises are empty and hollow promises to the people of this country."

But shadow business secretary Alan Duncan said the "astonishing" vote showed his party had won the argument.

He said: "The hunt will now be on for all those Labour MPs who have pretended to support their local Post Office and then done a runner when they had a chance to make a real difference."