The Conservatives will today call for MPs from across the political spectrum to condemn the government's plans to close post offices.
The Tories are using an opposition day debate protest against the planned closures and have challenged Labour MPs and ministers who have campaigned against closures in their own constituencies to oppose the nationwide policy.
Shadow business secretary Alan Duncan urged them to put their constituents above party politics.
Mr Duncan said: "We know which Labour ministers and MPs are against post office closures - we will see on Wednesday the true extent of their conviction."
Ministers argue the Post Office needs to make the cuts to reverse its weekly losses of nearly £4 million.
They have denied claims of hypocrisy, arguing it is possible to recognise the need for cuts across the country but oppose specific closures.
But Mr Duncan argued constituents would "simply not understand" why MPs could say one thing locally and still vote for closures.
The Communication Workers Union (CWU) has welcomed the vote but questioned the Conservatives' motives.
General secretary Billy Hayes said: "CWU believes the government has a
key role to play in protecting the Post Office network. We have consistently called for the suspension of the closure and franchising programme and welcome the parliamentary debate on the issue.
"However, we are concerned that the Conservative party does not have the best interests of the network at heart, as its policy effectively calls for it to be dismantled."
The mayor of London Ken Livingstone yesterday announced he would mount a legal challenge against 171 closures planned for the capital.
He said the Post Office had not given sufficient time for consultation and many closures would affect the most vulnerable Londoners.