New evidence has emerged linking the hormone-based drug Primodos to severe deformities or abnormalities in children, sparking fresh hope for families who have been campaigning for decades for compensation from its manufacturer.

Primodos was a hormone-based pregnancy test which detected pregnancy by inducing menstruation in women who were not pregnant.

A review by the Committee on Safety of Medicines in the 1970s concluded that the product should not be used by pregnant women.

But despite the evidence, no successful prosecution has ever been brought against the drug’s manufacturer, Schering-Plough.

A court case in 1982 collapsed after it was deemed unlikely that claimants could prove a direct causal link between Primodos and birth defects.

The papers, which were unearthed in the Berlin National Archives, include a study by Professor William Inman, a medical officer for the British Government, who was an advocate for tighter pharmaceutical regulation after the Thalidomide scandal.

The files show that Dr Inman had found that women who took a hormone pregnancy test were five times more likely to have a disabled child than those who did not take the drug.

The research was passed to the manufacturing firm, but was later destroyed by Dr Inman to prevent legal claims against the company being “based on his material”.

Yasmin Qureshi, a Labour MP who has supported those campaigning for an investigation into the effects of Primodos, told The Daily Telegraph: “These documents form a significant discovery and could lead to important developments.

“I believe there may have been a cover-up over the effect of this drug on pregnant mothers.”

Marie Lyon, whose daughter Sarah was born with a foreshortened arm, believes the tablets stunted her development in the womb.

Ms Lyon, chair of the campaign group Association for Children Damaged by Hormone Pregnancy Tests, said: “It’s unthinkable that more than 40 years after our children were born, neither the sufferers nor their mothers have had justice.”

Schering-Plough has now been taken over by Bayer. The company has said the use of Primodos in the 1970s was “in compliance with prevailing laws”.

The pharmaceutical giant maintains the “evidence for a causal association between the use of hormonal pregnancy tests and an increased incidence of congenital malformations was extremely weak”.

Bayer “rejects any suggestion” that anything has been concealed by Schering-Plough, other than privileged documents.

A spokesperson for Bayer said:

“Bayer denies that Primodos was responsible for causing any deformities in children.

UK litigation in respect of Primodos, against Schering (which is now owned by Bayer), ended in 1982 when the claimants’ legal team, with the approval of the court, decided to discontinue the litigation on the grounds that there was no realistic possibility of showing that Primodos caused the congenital abnormalities alleged.

Since the discontinuation of the legal action in 1982, no new scientific knowledge has been produced which would call into question the validity of the previous assessment of there being no link between the use of Primodos and the occurrence of such congenital abnormalities.”

A spokesperson for Bayer said: "Bayer denies that Primodos was responsible for causing any deformities in children.

"UK litigation in respect of Primodos, against Schering (which is now owned by Bayer), ended in 1982 when the claimants’ legal team, with the approval of the court, decided to discontinue the litigation on the grounds that there was no realistic possibility of showing that Primodos caused the congenital abnormalities alleged.