The use of a hormone pregnancy test in the 1960s and 1970s was not responsible for serious birth defects experienced by some families who took the drug, an official review has concluded.
The Commission on Human Medicines' (CHM) expert working group on Hormone Pregnancy Tests (HPT) said the scientific evidence it reviewed does "not support a causal association" between the Primodos test and birth defects.
It recommended that families who took an HPT and experienced an "adverse pregnancy outcome" should be offered genetic testing to see whether another underlying cause could be determined.
Marie Lyon, chairwoman of the Association for Children Damaged by Hormone Pregnancy Tests, told the Press Association: "We are bitterly disappointed that the Government has once again let people down who have relied on them to be open and transparent.
"It is similar to the previous inquiries which seemed more inclined to protect the reputation of government agencies and the drug companies rather than looking after the health of the populations of the UK."
The CHM said in a statement: "Following this extensive and rigorous review the overall conclusion, based on the totality of the data, is that the scientific evidence does not support a causal association between the use of HPTs such as Primodos and birth defects or miscarriage.
"In 2014 the Government committed to an independent review and having thoroughly examined all of the evidence, the conclusion of the review is that the use of HPTs, including Primodos, in early pregnancy was not responsible for serious birth defects experienced by some people."
It said clinical practice has moved on since the 1970s and there have been "far-reaching" advances in medical regulation but it made a series of recommendations to "further strengthen" systems for detecting, evaluating and communicating safety concerns for use of medicines in pregnancy.
These include: electronic side effect reporting, a working group to advise on better ways to collect and monitor data on the use of medicines in pregnancy and improving the impact of safety messages, monitoring their effect, and ensuring healthcare professionals and patients receive the best information about medicines in pregnancy.
In the past Ms Lyon, one of those who took the test, has argued there is "incontrovertible evidence" that the Committee on Safety of Medicines - an independent advisory committee to the UK medicines licensing authority - was "negligent in protecting the health of unborn babies".
Ms Lyon said the drugs she was instructed to take in 1970 were "40 times the strength of an oral contraceptive".
Her daughter Sarah, now 47, was born with a severe limb deformity with half of her arm missing below the elbow. Ms Lyon, 71, said: "I didn't ask because I assumed that was the way that you found out you were pregnant.
"But I wasn't given a choice, I was just given these two tablets, told to take them and then if nothing happened I was pregnant.
"When Sarah was born she was born with her arm missing from just below the elbow but there was a tiny little palm with five little tiny fingers which they had to amputate when she was 13 months old so she could have an artificial limb fitted.
"But she was extremely lucky - some of our members have got young adults in wheelchairs, they are incontinent, some are blind, brain damaged, it is dreadful. She is exceptionally lucky and so am I, in comparative terms."
The Association represents 236 families who believe they were affected by taking the drugs in early pregnancy.
It estimates that 1.5 million took the drugs and thousands of families have been affected, though some may be unaware.