Union leaders reacted with scorn to Royal Mail's public apology to Oxfordshire customers printed in an advertisement in yesterday's Oxford Mail.

The advertisement said: "Royal Mail today issued an apology to all its customers as the unofficial industrial action by some employees at the Oxford mail centre entered its ninth day. The strike is unlawful and is causing great disruption to you, the customer."

Bob Cullen, of the Oxford branch of the Communication Workers Union, reacted by saying management was being "sparse with the truth".

He said: "If they were serious about concern for the customer, we would be in there now negotiating.

"We don't like being out here but I have not met management since Saturday."

The union contends that bullying and harassment by a certain group of workers reached such levels that it became a safety issue.

The advertisement continued: "The concerns of staff about safety and harassment are being dealt with professionally and as a matter of urgency."

Mr Cullen said: "Yes, they have taken steps to make it safer, but it took seven days of strike action to make them do it."

Royal Mail said: "The strike is continuing because we are now refusing to pay overtime to the people who are taking unlawful action."

But Mr Cullen said: "They want to penalise the very people who brought increased safety to the work place."

The union plans to hold a mass meeting today (April 8), the tenth day of the strike, to decide whether to continue.

Chairman of watchdog Postwatch Midlands, Richard Ward, said: "The fear is that the strike could escalate."

Business leaders said the wildcat post strike was beginning to affect the local economy.

Chairman of the Oxfordshire Chamber of Commerce Keith Slater said: "Cash flow problems are arising through cheques getting caught in the post.

"Businesses are taking time-consuming and expensive measures to counter the strike. Some business people are going out of the area to collect goods and post mail. Others are arranging to be paid by telegraphic transfer."

Estate agents and solicitors are among businesses hit by the strike.

A spokesman for business lawyers Manches said: "The dispute is proving to be a great inconvenience."

A spokesman for estate agents Cluttons said: "People are complaining that they are not getting particulars of houses."