Tesco Christmas promotion had claimed that, "www.tesco.com is 10 percent cheaper than Amazon.co.uk on chart books."

The Advertising Standards Authority (ASA) is reported to have said on Wednesday that “Tesco failed to clearly specify which products were cheaper and whether they were available exclusively in stores, on its website, or both. “

It was Amazon.co.uk filed the complaint against Tesco after the ads, which first appeared last October. The ads ran in national newspapers, in brochures circulated at the supermarkets and on Tesco.com.

An Amazon spokeswoman was reported to have said, “it was the first time the company has challenged a competitors' pricing claims in the UK. “

Amazon has become the world's largest online retailer, staking out a reputation as having a larger product selection and cheaper prices than competitors.

Tesco, meanwhile, has built a profitable online business in Britain, aggressively positioning itself as a recognisable substitute for Amazon.

While the Advertising Standards Authority (ASA) has found that Tesco.com’ s claims where misleading, the ruling carries no penalty. Does this ruling by the Advertising Standards Authority (ASA) give advertisers cart blanch to say what they wish with out fear of reprisals?