A humble British coffee roasting company was the latest target of Internet share "punters and dumpers" this week, but financial regulators said they had yet to catch up with any illegal share rampers.

Shares in Coburg Group suddenly doubled on Tuesday afternoon after an anonymous tipster on an Internet bulletin board suggested that the company's management was about to transform the company into a tasty Internet concern.

This appeared to be news to Coburg's board, which said it was unaware of any reason for the share price rise, but not before hundreds of investors had piled into the stock, pushing turnover to over 35 million shares and making it the fourth most active stock in the London market, eclipsing even blue-chip giants like BP Amoco and Tesco.

Coburg shares fell some of the way back to earth on Wednesday, dropping 28 per cent, but an Internet tipster in the know could still have doubled his money.

Britain's financial watchdogs said there was nothing novel about this type of potential stock market abuse, only now the dingy corners of 18th century coffee houses have been replaced by anonymous Internet chat sites or bulletin boards.

Manipulating share prices - or "punting and dumping" as it is now known - is illegal wherever it occurs, and could land the individual in jail for up to two years.

However, so far perpetrators, ducking and diving through cyberspace, have managed to avoid the long arm of the law.

All three regulatory bodies said they were following the example set by US watchdogs, and now had teams of people and machines trawling through the backwaters of the Internet in search of dubious goings on.

The London Stock Exchange even has a high-tech search engine dedicated to sniffing out market abuses in cyberspace.