The Post Office is facing High Court action over alleged late delivery of tender documents.

One of the country's top private market-operating companies is suing it for more than £340,000 after tender documents concerning a market at Port Talbot were discarded by the local authority because they arrived after the deadline.

Wendy Fair Markets, of Uxbridge, Middlesex, claims that as a result of the delay it lost the opportunity to be considered as potential operator of Port Talbot market.

Now the company, which claims to have lost profits of £346,446.21, is seeking damages in what could turn into a sign-post action on the public's rights to sue the Post Office.

The company says it sent the tender documents through the Parcelforce Datapost Service on 24 November, 1995, to the town clerk at Port Talbot Borough Council, and that these should have been delivered by 10am the following day.

But it says the tender was delivered four days late – and that as a result the council returned the tender document, saying the bid would not be considered because it was received outside the closing date.

Wendy Fair will claim when the case gets to court that the council's usual policy is to award contracts to the highest tenderer – and that the council had confirmed that Wendy Fair's tender was the highest.

The company bases its loss estimate on the fact that it had run the market in the past and so has detailed knowledge of its finances.

Wendy Fair director Ken Hobday says: "We used to run Port Talbot market, but lost it when it was put out to tender on a previous occasion. Because of our past experience running the market, however, we are in a good position to assess the amount of money we consider we would have earned had our tender been received on time."

Isadore Goldman is acting for Wendy Fair.