The European Union's antitrust watchdog, has been investigating the firms' practices for years amid suspicion of price-fixing and the carving up of markets in Sweden, Denmark, the Netherlands, Germany and Austria.

Rival Swedish firm Powerpipe has said the existence of the cartel was common knowledge in the industry. Besides ABB, the companies concerned are Logstor, Tarco and Starpipe of Denmark and Germany's Panisovit and Isoplus.

Under 1997 guidelines the commission can fine companies guilty of cartel operation a base sum of 20 million Ecus ($23.93 million). But amounts actually levied in cases since then have been higher and lower depending on whether a company was ringleader or not, its size and the seriousness and duration of the infringement.

Under EU legislationfines cannot go beyond 10 per cent of a company's total annual sales, a threshold which has never been approached.

Last week the commission fined British Sugar 39.6 million Ecus for conspiring on prices in Britain with other companies, all of them hit with much smaller amounts.

In September it slapped a total record fine of 273 million Ecus on 15 shipping firms, with the highest penalty for P&O Nedlloyd (41 million Ecus).

Volkswagen holds the record for the biggest EU fine on an individual company at 102 million Ecus.