Card crime in Scotland's convenience stores has risen by 54% since the introduction of chip and pin in credit and debit cards, it was revealed last night.

Around £143,425 worth of goods have been fraudulently obtained, the Scottish Grocers' Federation (SGF) Retail Crime Survey for 2006 shows.

SGF is the umbrella organisation of Scotland's 5500 convenience stores and represents retailers including all the Scottish Co-ops, Somerfield, Spar and local independents.

The findings are the first stage of an investigation into why the chip and pin system appears to be failing its members' shops while at the same time reducing card crime in other stores.

The survey organisers admit they have no answers and will be going back to the 1000 members surveyed to investigate the problem further.

There have been theories that as some corner shops are small, would-be thieves are looking over the shoulders of people who use chip and pin card machines. They memorise the number then try to steal the card at a later date.

Others believe that thieves simply use stolen credit cards in a number of smaller shops rather than big ones to avoid attracting attention.

Gordon MacRae, of the SGF, said: "We will be asking more questions to get to the bottom of the problem. To have such a high rise in the amount of fraud is a finding we did not expect. We have no answers, but will continue to look into the matter.

"We will be asking our members to put the credit card in the machine for customers rather than let them do it themselves."

Other figures showed there were 78,257 customer thefts across stores in Scotland; 137 reported burglaries resulting in £148,083 of lost stock; 263 incidents of physical violence against staff; 5099 threats of violence and 334 racist incidents in the second half of 2006 alone.

Cheque fraud cost stores £5273, which is significantly lower than previous years, although this can be seen to be a result of many stores no longer accepting cheque payments. Around £4160 in counterfeit money passed through convenience store tills in 2006.

John Drummond, SGF chief executive, speaking as he opened its 2007 conference in St Andrews, said: "We were shocked at the staggering rise in card fraud despite the introduction of chip and pin which was supposed to stamp out credit and debit card misuse.

"There are no clear reasons for this rise and SGF will be undertaking further research with our members before seeking urgent talks with card issuers to tackle the problem."