Retailers face the bleak prospect of extra costs and even longer working hours over the holiday period in order to meet the deadline for reinstating the 17.5% VAT rate.

The tax rate reverts to its higher level from January 1, 2010, forcing retailers to put in more working hours to make the changes at a time when staff are usually reluctant to work shifts.

Trade bodies have criticised the government over the confusion that moving to the higher rate of VAT will cause.

"A situation where some 'old' shelf prices are less than the 'new' price that a customer is asked to pay at the till could be more difficult for retailers than when the VAT rate was reduced," said British Retail Consortium (BRC) director of business environment Tom Ironside.

Association of Convenience Stores (ACS) chief executive James Lowman said that forcing retailers to change their prices by New Year's Day would cause havoc. "The decision to reinstate a 17.5% VAT rate on January 1 will cause major and costly disruption for retailers on a bank holiday, in the middle of the busiest trading period of the year," said Lowman.

The ACS had called on the government to delay the VAT change until February 1, 2010, to limit the amount of disruption caused. The government declined to do this, but has published a consultation on its intention to increase from 14 to 28 days the amount of leeway retailers will be given display old price tickets. The consultation is due to close on November 23.

Although the consultation was welcomed by the ACS and the BRC, retailers say that it is a hollow gesture as prices will still have to be changed by January 1, and having inaccurate prices on display will simply cause confusion at the checkouts.

William Brown of Frankmarsh Stores in Devon said that if there was a difference at the till, customers would want to pay the lower price. "It was fine last year when prices were cheaper at the till, but if they are higher then they won't be happy," he said.

"We wrote to the government asking it to delay the VAT change until February, but it told us that it would cost £8m, so instead we have to work harder and fork out."