TESCO apologised to customers today after a computer glitch caused the tills to stop working at about 100 of its supermarkets.

Shoppers around the country faced lengthy queues to pay for their goods and a small number of stores had to close because of the bug.

Problems were reported across the UK, including at Tesco shops in York, Birmingham, Liverpool, Edinburgh, London, Ashford, Workington, Mold and Northern Ireland.

The glitch, caused by an overnight computer update, crippled the stores' main tills but did not affect self-service checkouts.

Tesco said around 100 of its 2,184 UK supermarkets were hit by the problem and stressed only a ''handful'' were left unable to serve shoppers.

A spokeswoman for the company said: ''Tesco has apologised to customers for any inconvenience caused as a result of a computer problem which caused tills at some stores to stop working for a short time today.

''The problem was quickly identified and fixed within minutes, meaning only a handful of stores could not serve customers.

''Most stores were either unaffected or able to use their self scanning checkouts which were not affected by the computer glitch.

''Extra staff were allocated to these checkouts to ensure customers could continue shopping with the minimum of disruption.

''Home deliveries were unaffected and any petrol filling stations involved continued serving customers through 'pay at pump', which is available on the vast majority of pumps.

''The computer problem was traced to an error in a routine system upgrade sent to stores overnight.''

The computer glitch came as Tesco gave its Clubcard loyalty scheme a £150 million relaunch.

A spokesman refused to confirm how much the problem had cost the supermarket giant in lost business.