A shopper whose handbag was snatched outside a supermarket by a bicycle-riding thief has called on the store to improve its security.

The woman from West Oxford, who asked not to be named, was loading shopping into her the boot of her car outside the Sainsburys store in Heyford Hill, Oxford, at 10pm on Friday, when the thief opened the passenger-side door, removed the bag and pedalled off.

The bag contained £70 in cash, credit cards and a cheque book. The 42-year-old woman was left shaken by the theft and called for security to be stepped up at the supermarket.

Her husband said: "My wife was devastated. The thief must have been watching, as he knew where she had put the bag. It was very unpleasant and could happen to anyone.

"Security inside the store may well be good but outside it is poor. Security staff are more interested in looking after their property inside than the safety of their customers in the car park. People are being encouraged to shop at night but more should be done to make the area safer.

"The moment you step outside you are in a dangerous environment."

The theft followed a similar incident earlier this year in which a woman shopper had her bag snatched outside the supermarket. There have also been thefts at the Tesco store on the Oxford Retail Park in Cowley.

Paul Witham, duty manager at Sainsburys, said the car park was patrolled by security guards. He said: "We are doing everything we possibly can to improve security, though we are open to suggestions. We care about our customers. Not even half of one per cent of thefts occur in the car park."

Sainsbury's is planning a week-long blitz on thieves and shoplifters, by flooding the store with security staff. Mr Witham described the initiative as a "zero tolerance" campaign and insisted the car park would be under close watch.

Staff have also put up posters warning shoppers to look after their property.