'Send your Christmas cards now to avoid the mail strike'

Postal workers have warned that Christmas cards and gifts may not arrive in time if they are not sent within the next three weeks.

The Communication Workers Union said its forecast would be realised unless Royal Mail reached an agreement to resolve industrial action that has crippled the network.

A backlog of tens of millions of letters and parcels has built up as a result of rolling strikes, and union leaders say a million may never be delivered.

Pictures of "mail mountains" at a distribution centre in Dartford have been accompanied by claims of letters posted a month ago lying untouched. Martin Walsh, the CWU's London representative, said: "Unless we get an agreement by the second or third week of October, the backlog is so big that it will impact upon Christmas.

"Royal Mail has drafted in managers, but all they're trying to do is to clear the mail that has been posted recently."

Postal workers have been staging regional strikes for months in a dispute over jobs, pay and services. London has been one of the worst affected areas, with 65 per cent of Britain's mail passing through the capital. The CWU is balloting 121,000 workers to hold a national strike in the run-up to Christmas.

Royal Mail said: "We are focused on delivering excellent customer service over the vital run-up to Christmas."