The Northminster toilets now cost 20p each time for both market workers and shoppers, after the fee was brought in by Peterborough City Council.

Council chiefs argue that the charge will ensure the top-rated public conveniences are kept at their sparkling best.

But stallholders at Peterborough market said it would hit trade.

Chairman of the market committee Akbar Dhanji said: "I am not very happy with it at all to say the least. This cost is yet another expenditure on our business and we have no way of claiming back the money that we spend.

Mr Dhanji, who owns the Simply Fabrics stall, added: "The toilets are much cleaner than they used to be, so I understand we are paying for a service, but I am still disgusted at the amount of money I am going to end up forking out."

Stall owner Sue Wesley (46) said: "Trade has already decreased recently due to the rising car parking charges, the credit crunch and many other reasons, and this is not going to help.

"People will stop coming up to this end of town as going to the toilet is a necessity that people will not want to pay for. I am especially concerned for our elderly customers. It is ridiculous."

She said that although there are two toilets on site for staff to use, this was not enough and they often ended up using the Northminster toilets.

Peterborough City Council's head of operations David Denson said: "The city council spent more than £200,000 modernising the Northminster toilets in 2006.

"Prior to this, we received regular complaints from the general public and the Market Traders' Association relating to the standard of the toilets.

"A 20p charge was introduced following the refurbishment works so that the toilets could be staffed by attendants.

"This has enabled the facilities to remain in good condition which has been recognised by the British Toilet Association with the awarding of Five Stars in the Loo of the Year Awards 2008."

The council said even its own employees were not allowed to use the facilities free of charge, so they could not make any exception for the market traders.

The market committee has proposed the idea of traders paying a one-off fee for tokens.

Mr Dhanji said: "This way at least we will only be paying once and we will have a proof of spending to claim our taxes back on."

It is thought about 200,000 people visit the city centre's Car Haven and Northminster toilets each year, potentially generating £40,000 – money which will be ploughed into the upkeep of the five-star Car Haven and four-star Northminster toilets.