By 1988 about 400,000 Britons were thought to be dependent and they remain the most commonly misused prescription drugs in Britain.
Now, however, the victims of addiction to tranquillisers such as Valium and Ativan are fighting back through the courts.
Reg Peart, a former atomic scientist, is one of those hoping to win compensation from the manufacturers.
Now 62, he began taking Valium in his late 30s for attacks of nausea and vertigo and has only latterly begun to piece his life back together. As his addiction took hold he lost his career, his marriage, and ended up one step from living on the streets. He says that at his lowest point he had a mental age of 10. The only reason the majority of people continue to take benzodiazepines for more than a few months, he believes, is because they are addicted.
When he was eventually, abruptly, taken off the drug in 1985 he went into cold turkey and given repeated electro-shock therapy to treat his withdrawal symptoms. It took until 1992 until he began to feel right, although tests showed he was still suffering 20 per cent intellectual impairment. "It was like a car running on low-grade petrol and then it runs out. The car won't start."
A number of the litigants in person suffer from agoraphobia and most do not work. Michael Behan, a 42-year-old former teacher, began taking Ativan in 1981 after getting panic attacks in lifts and underground trains. He says he became addicted in a couple of months, but his doctor took the view that his original illness was getting worse.
"You are told you are not addicted and you can't understand why you feel so awful if you stop taking it. So you stay on drugs year after year." The addiction lasted seven years.
However, where the ultimate responsibility lies is unlikely to ever be tested in a British court.
Up to 40 victims plan to press on with their claims against the makers of Valium and Ativan, despite the spectacular collapse of what was once tipped to be the biggest group negligence action ever.
The claimants are facing an uphill task to persuade the Court of Appeal to reverse a little-noticed decision last month in which Mr Justice Ian Kennedy, the High Court judge in charge of the litigation, struck out the remaining 70 writs in an action originally numbering more than 5,000.
Dr Peart and other claimants in the Victims of Tranquillisers group are protesting that the striking out was unfair because it was due to early problems in the organisation of the group action, not on the merits of individual cases.
If necessary, the complaint will be pursued to the European Court of Human Rights, Dr Peart said.
Last month's ruling was the latest of a series of blows to claimants in the benzodiazepine litigation which was launched in 1988 on behalf of thousands of Britons who had become dependent on Valium, Ativan and other tranquillisers and sleeping pills in the benzodiazepine group.
More than 17,000 people came forward and 13,000 were initially granted legal aid after a group of lawyers announced plans to sue the multinationals which developed and marketed the drugs on the ground that they should have known about the risk of addition and warned of it. The Government had warned in 1988 that prescriptions should be longer than two to four weeks.
But after the Legal Aid Board withdrew funding for claims against Roche Products, makers of Valium, Mogadon and Librium, in 1993 and for those against John Wyeth and Brother, makers of Ativan, the following year, the group litigation effectively collapsed.
Around pounds 35m of public money had been spent on legal costs without a penny reaching those who claimed to have been damaged through taking the drugs. The 70 had soldiered on, all bar one as litigants in person without legal representation. But Mr Justice Ian Kennedy struck their claims out as an "abuse of process" because, among other reasons, the Legal Aid Board had deemed them not reasonable to support and the costs of a complicated and strongly contested trial would be enormous compared with any small amounts of damages recovered. There had also been "inordinate and inexcusable delay" in progressing the cases.
The two drug companies, which have always strongly denied liability, and had hoped that the July decision would finally close the issue, promised they would not enforce orders for costs they have been granted since legal aid was withdrawn - but on condition that the 70 litigants do not appeal last month's ruling. About 30 are expected to conclude that they would risk losing assets such as their homes, but up to 40 consider they have nothing to lose.
In any event, claimants would have to exhaust all their UK legal remedies before applying to Strasbourg. The Legal Aid Board refused funding for the appeal last week.
Article 6 of the European Convention on Human Rights says that "in the determination of his civil rights . . . everyone is entitled to a fair and public hearing within a reasonable time". Dr Peart said the litigation had showed that the English legal system was totally inadequate to cope with group actions. In the United States drug companies have paid out billions of dollars to patients claiming they were injured by their products. In Britain no group action against a commercial company has reached trial, although the 1,200 victims of the Opren anti-arthritis drug secured pounds 2.275m in an out-of-court settlement in 1987.
The remaining claimants complain that they have been denied the right to pursue their actions because the costs would dwarf any damages. The root of the problem was that investigation of cases viewed as unwinnable both slowed down the progress of the case and clocked up enormous costs.