A 24-hour strike planned by postal workers in five mail centres, which would have threatened disruption to Christmas deliveries, has been called off, it was announced.

Members of the Communication Workers Union in Crewe, Coventry, Bolton, Stockport and Oxford had planned to walk out in a row over office closures.

The union had originally threatened strikes in seven offices, but workers in Oldham and Liverpool called off their action earlier.

Dave Ward, deputy general secretary of the CWU, said: "For the last five years we have been fighting attempts by Royal Mail management to chip away at the foundations of a universal postal service.

"We are calling off the strikes as some progress has been made, justifying the continuation of more meaningful discussions."

Mr Ward said the Government's plans to partially privatise the Royal Mail meant the stakes were "even higher", adding: "This is no longer a local or regional dispute. What we face is the prospect of losing a much loved British institution. We want the public to join with us in a nationwide campaign to defend a vital public service."

A ministerial aide quit on Wednesday in protest at the Government's plans for the Royal Mail and a number of backbench Labour MPs warned they would fight to keep the organisation wholly publicly owned.

Jim McGovern, who resigned from his position as Parliamentary Private Secretary (PPS) to Business Minister Pat McFadden, said: "I believe a PPS has to be fully supportive of proposals of the department which they serve. In this case, I do not support what looks to me like partial privatisation of the Royal Mail.

"In his statement Pat McFadden said he welcomed an expression of interest from the Dutch postal company TNT. "For me, it simply beggars belief that we would employ the services of a company from abroad to tell the Royal Mail in this country where they are going wrong."

A Royal Mail spokesman said: "We are very pleased that all our people will be focused on delivering the Christmas mail for our customers."