An Oxford sub-postmistress has hit out at the "Scrooge-like" attitude of the Post Office in ordering people to work later on Christmas Eve.

Sub-post offices, which are privately run, will not be joining the strikes at Oxfordshire's five main Crown post offices, called by the Communication Workers Union.

But one sub-postmistress, who did not want to be named, said they were annoyed at the "bullying" tactics employed by the Post Office management.

The Federation of Sub-postmasters said its suggestion of a voluntary opening, depending on whether there was demand from customers, had been rejected by the Post Office.

The Oxford postmistress said: "We have been told that if we close before 4pm, we will be in breach of our contract and action may be taken against us. The Post Office is going to check our computer system to establish what time we log off.

"Post Office Ltd has lost most, if not all, goodwill with sub-postmasters, who only stay because they enjoy the work and service we provide, but the constant bullying by Post Office Ltd is making life unbearable."

She accused the Post Office of acting in a "Scrooge-like manner" and said her office would probably not have any customers after 12.30pm on Christmas Eve.

Post Office spokesman Jane Thomas said the Christmas Eve opening times were published on November 11 in a magazine sent to sub-postmasters.

She said: "Post Office Ltd wrote to all sub-postmasters across the country on December 14 confirming these opening times.

"Our sub-postmasters have contracted hours they have to open and it's not unreasonable for Post Office Ltd to ask our agents to stay open to meet the needs of our customers."

The Post Office has pledged to open strike-hit offices by using non-union staff and managers. It has set up a helpline, 0845 722 3344, giving details of which offices will open until 4pm.