Calls were made yesterday to stop half of all high street post offices being closed or sold off under plans being considered by the Royal Mail.

As many as 270 offices could be shut down or offered to local consortiums as part of reforms being discussed with unions and consumer groups.

Dave Ward, the Communication Workers' Union (CWU) deputy general secretary, said the Government should support the "unrivalled service" of the Crown post offices.

They have an integral role in communities up and down the country which must be protected, he said.

The plight of the Crown post offices, run directly by Royal Mail, will be investigated later this month by the Trade and Industry Select Committee. A decision is expected on the future of all 560 branches before the end of the financial year.

Andy Furey, who is leading the union's negotiating team during the talks with Post Office Ltd, said they were still seeking to secure a viable future for the post office network in the face of closures and selling off of franchises."

The CWU represents 7,000 workers in Crown offices and more than 160,000 in the postal industry.

A Royal Mail spokesman said: "Post Office Ltd has not reached a decision about the future of the 560 Crown post offices, but we confirmed a shortfall of £70m in the last year."

Crown post offices, which have no postmasters and are usually in high streets, could command vast sums if sold off for commercial use.

Former sites in Glasgow and south London have already been put up for sale and other branches in major cities could follow.