A fresh Microsoft monopoly storm is brewing, following accusations levelled at the company over the bundle of features in Windows XP, its latest operating system.

Two of the state attorneys general who led the US Justice Department's antitrust case against Microsoft on Wednesday fear the company may be "repeating its efforts to maintain and extend its monopoly".

Critics say the company is reverting to old tactics by loading Windows XP with features such as instant messaging and smart tags, which give Microsoft greater control over consumers' Internet use.

Richard Blumenthal, attorney general of Connecticut, and Tom Miller, attorney general of Iowa, issued a strongly-worded press release on Wednesday, saying they had "serious concerns" about Microsoft's "very troubling" strategy for its Windows XP operating system, which will be launched this autumn.

"Microsoft seems to be using much of its power to preclude competition on a new platform," said Mr Miller, who organised the original 19 attorneys general that joined the Justice Department in the current antitrust suit.

Their statements follow mounting pressure from antitrust experts, who claim that Microsoft is still using the type of monopolistic practices that sparked the original antitrust case, which is currently under review by the US District Court of Appeals.

Microsoft's decision to bundle its Web browser, Internet Explorer, was the basis for the antitrust case now under appeal.

Mr Blumenthal and Mr Miller dismissed earlier reports by the Associated Press in the US, which said that the pair were preparing to file a second antitrust lawsuit against Microsoft.

"We have no current plans for a second lawsuit," the attorneys general said in their statement. "We would never completely rule out a new suit, but our focus now is on the antitrust case that already is before the courts," they told the Financial Times.