Plans to privatise Royal Mail should be postponed to prevent an even deeper crisis for Britain's post offices, the Government has been warned.

The National Federation of SubPostmasters (NFSP) wants a delay to the controversial sell-off amid "serious concerns over the future of the post office network".

George Thomson, general secretary of the NFSP, said post offices faced an "extremely uncertain future due to an appalling lack of new work", as he called for more to be done to ensure the network has a viable future before Royal Mail is sold.

The NFSP fears a privatised Royal Mail would not feel obliged to keep services in the Post Office network.

In a speech to delegates at the NFSP's conference in Torquay, Mr Thomson said: "We must have confidence the network can survive without Royal Mail before it is sold off. Currently, if privatisation goes ahead, the Post Office will be left in an even deeper crisis. It will be a company set up to fail.

He went on: "For the last three years we have been working with the Government to try and secure essential new work for subpostmasters, but the Government has failed abysmally to deliver. In fact, subpostmasters are now earning less from Government services than they were three years ago, which is a damning indictment.

"For this reason, the NFSP is today calling for an immediate delay in plans to privatise Royal Mail."

Currently, the Post Office receives millions of pounds a year from Royal Mail to deliver key services.