US regulators today launched a legal action against Intel, amid fresh accusations that the computer chip maker deliberately stifled competition.

The announcement by the Federal Trade Commission, which oversees the enforcement of competition law in the US, marks the latest in a series of worldwide antitrust cases against the Californian technology company - and is the most significant action taken by the regulator since it took Microsoft to court in the 1990s.

The FTC said that its decision to sue Intel comes after a long string of allegations that the company forced and coerced computer manufacturers to use its technologies instead of those made by rival companies.

"Intel has engaged in a deliberate campaign to hamstring competitive threats to its monopoly," said Richard Feinstein, who heads up the FTC's bureau of competition.

"It's been running roughshod over the principles of fair play and the laws protecting competition on the merits. The commission's action today seeks to remedy the damage that Intel has done to competition, innovation and, ultimately, the American consumer."

Among the allegations are claims that the company offered discounts to customers like HP, Dell and IBM on the condition that they drop products from its main rival, AMD. The company is also accused of deliberately deceiving its customers and "smothering" potential competitors.

Intel has responded by calling the case "misguided" and suggesting that some of the allegations had been added after earlier negotiations to settle the case out of court had reached an impasse.

"The FTC's case is misguided," it said in a statement. "It is based largely on claims that the FTC added at the last minute and has not investigated. In addition, it is explicitly not based on existing law but is instead intended to make new rules for regulating business conduct. These new rules would harm consumers by reducing innovation and raising prices."

In a briefing with reporters, Intel's general counsel Doug Melamed argued that the FTC was overstepping its legal mandate.

"Some of these issues were brand new to us," he said. "It seems to me that the FTC is seeking to restrict all kinds of pro-competitive price discounting."

The lawsuit, he said, was designed to unfairly restrict the activities of large companies offering legal discounts to customers "and from protecting their intellectual property rights by controlling their licensing and preventing others from taking advantage."

The case comes after similar actions against Intel in other jurisdictions, including a case brought by the New York attorney general Andrew Cuomo and a record €1.06bn fine from European regulators who accused the company of "harming millions of European consumers".

It also follows the news last month that Intel had agreed a $1.25bn settlement with AMD, its major competitor, to bring to an end a series of complaints about its business conduct.

Much of the FTC's case against Intel is similar to the one heard in Brussels, which produced evidence that the company had spent millions paying companies to avoid AMD's products - and against which Intel is appealing. However, American officials also added new allegations to the mix by saying that Intel had also presented certain performance information in a way that misled both customers and competitors.

"Intel secretly redesigned key software, known as the compiler, in a way that deliberately stunted the performance of competitors' CPU chips," the commission said. "Intel told its customers and the public that software performed better on Intel CPUs than on competitors' CPUs, but the company deceived them by failing to disclose that these differences were largely or entirely due to Intel's compiler design."

The case significantly expands on previous claims by including not only CPUs - the central processing units that form the brain of the modern computer - but also GPUs, the chips used to power computer graphics. While AMD is Intel's main rival in the CPU market, other companies compete against Intel in graphics, including Nvidia and Via.

"We applaud today's action by the US Federal Trade Commission," said Nvidia in a statement. "We are particularly pleased to see scrutiny being placed on Intel's behavior towards GPUs, which have become an increasingly important part of the PC industry."