June 2 (Bloomberg) -- Barclays Plc and Royal Bank of Scotland Group Plc were raided by the U.K. antitrust regulator as part of an investigation into the price of loans to accountants, lawyers and other professional services firms.

The two banks were visited 12 days ago, Corinne Gladstone, a spokeswoman from the Office of Fair Trading said in an interview today. London-based Barclays said it approached the OFT with information about ``inappropriate'' contacts with one department in exchange for leniency on March 17.

The issue is the second involving U.K. banks to come under OFT scrutiny in the last year. In April, a High Court judge ruled that the regulator could legally challenge the overdraft fees of eight banks, including Barclays and RBS. The banks are currently appealing the court decision.

``The last thing the U.K. banks need right now is additional pressures on their share price from internal issues,'' said Mamoun Tazi, an analyst at MF Global Securities Ltd. in London, who has a ``sell'' rating on RBS stock and a ``buy'' rating on Barclays. ``It doesn't bode well. It could undermine a big chunk of their business. The banks could be putting out regulatory fires on several fronts.''

RBS said in a statement that it is cooperating with the probe and declined to comment further.

`Stops There'

``The investigation is operating within the confines of the Professional Services banking area and we believe that, if there is any issue, it starts and stops there,'' Alistair Smith, a spokesman for London-based Barclays, said in a statement.

Barclays' shares fell 9.5 pence, or 2.5 percent, to 365.5 pence in London trading today. Edinburgh-based RBS fell 2.5 pence, or 1.1 percent, to 226 pence.

Gladstone said RBS and Barclays were the only banks targeted in the raids, describing the investigation as ``narrow.''

``The OFT's investigation is at an early stage,'' the regulator said in a statement.

This is the fifth major price-fixing investigation the OFT is undertaking, after probing supermarkets and the construction industry.

`Pandora's Box'

``From both the European Commission and the U.K. regulators' point of view, the financial services sector has been like a Pandora's Box: they want to have a look, but they don't want to lift the lid,'' said Mike Pullen, an antitrust lawyer at DLA Piper in London. ``The OFT has been very clever here in going for a narrow focus: it makes it more manageable.''

If found guilty of price-fixing, the banks could face a fine of as much as 10 percent of their global revenue from the affected market.

Barclays said it had approached the regulator for leniency. Under the OFT's leniency program, the first company to come forward can be completely protected from a fine. In February, the regulator also started a reward program for whistle-blowers, offering as much as 100,000 pounds to informants who provide information about price fixing.

``Barclays shows that the OFT's leniency program is bearing fruit,'' Pullen said. ``With the credit crunch, you can expect more scrutiny of the financial services sector, more appeals for leniency, and more disaffected employees blowing the whistle.''

To contact the reporters on this story: Caroline Binham in London at cbinham@bloomberg.net.

Last Updated: June 2, 2008 12:39 EDT