The companies accused of fixing the price of common prescription medicines have dismissed the claims.
The case centres on common prescription drugs
The seven companies say they will vigorously defend themselves when the case comes to court.
The NHS is suing Norton Healthcar Ltd UK, Norton Pharmaceuticals, Regent-GM, Kent Pharmaceuticals, Generics UK, Ranbaxy UK and DDSA Pharmaceuticals.
It alleges that the companies colluded to fix the price of some drugs.
It claims it paid over the odds as a result and is seeking compensation.
However, the companies have vowed to fight the case.
Norton Healthcare said any increase in the cost of these drugs was partly due to new European regulations on packaging.
It said it was confident it would win the case.
"The company firmly believes that sales of penicillin-based antibiotics during the period 1996 to 2000 were in compliance with all applicable laws and
regulations, despite the High Court claim issued by the Department of Health," said a spokeswoman.
"While strongly refuting the allegation, the company is co-operating fully to provide all the relevant information to repudiate this claim."
A spokesman for Ranbaxy UK said: "We do not believe that we have behaved in an improper way and will defend the legal proceedings vigorously."
Regent-GM Laboratories said it would be defending the case. A spokeswoman declined to comment further.
Kent Pharmaceuticals said: "The company has not acted unlawfully in any of its dealings with the NHS and will vigorously defend all of the claims."
It said the majority of claims relate to price changes in 1999, a year of great turbulence for the generics market caused by a number of factors outside
the firm's control.
These included the closure of Regent Laboratories in December 1998, which had
been a significant manufacturer of both penicillin and warfarin, and millennium bug fears which caused stockholders to carry abnormally high levels of stock.
"None of these factors has been taken into account by the Department of Health in formulating their claims," it said.
"It is unfortunate that the government is persisting in this
sustained attack on an industry that has and continues to deliver annual saving
of billions of pounds to the NHS."
The other companies involved in the case were unavailable for comment.