The Conservative Party will call for the suspension of the controversial closure of 2,500 post offices because of the "concern and unpopularity" the plans have caused.
An opposition day debate in the Commons will highlight protests against the closures, which have included demonstrations across the country as well as legal moves to keep branches open.
Shadow business secretary Alan Duncan will urge Labour MPs to "put constituents above party politics" by supporting calls to have the closures re-assessed.
The Conservatives said a number of Labour MPs and ministers had campaigned against branch closures in their own constituencies.
Six branches in Waltham Forest and and five in Redbridge are earmarked for closure.
"We know which Labour ministers and MPs are against post office closures - we will see today the true extent of their conviction.
"It is all well and good Labour MPs issuing warm words but now we have a chance to act together to save our post offices.
"Their constituents would simply not understand how they could say one thing locally, and then not vote in support of saving their post offices when given the chance.
"Hundreds of thousands of people will be badly let down if MPs put party politics ahead of the concerns of their constituents," said Mr Duncan.
Tory leader David Cameron visited a post office in Hammersmith, west London that has been earmarked for closure, while a number of celebrities, including comedienne Victoria Wood, joined a protest against the closure of a branch in Highgate, north London.
Ms Wood, who has lived within walking distance of the post office for 15 years, said she could not understand why the Government was prepared to "destroy" local life.
Copyright Press Association Ltd 2008, All Rights Reserved.
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