The damaging drug may have been developed as an antidote to nerve gas.

The morning sickness drug thalidomide, which caused pregnant women to give birth to babies without arms and legs, was first developed by the Nazis, probably as part of their chemical weapons programme, according to new research. Two separate academics have revealed the discovery of documents indicating that the drug did not originate with Chemie Grünenthal, the postwar German chemical firm, as has always been claimed.

If, as their research suggests, thalidomide was first developed by scientists working in wartime Germany, it could have implications for the liability of the German government. So far it has given compensation only to German victims, although the drug was distributed in at least 46 countries.

Thousands of the drug's victims are still battling for increased financial aid to help them cope with its legacy. There are 457 thalidomiders remaining in the UK; 2,700 in Germany; and a total of up to 6,000 worldwide.

Mothers prescribed it between its launch in 1957 and 1961, when it was removed from the market, gave birth to children who lacked proper arms, legs, hands and feet. Some had also suffered brain damage and other disabilities.

Dr Martin Johnson, director of the Thalidomide Trust which provides help for surviving victims in the UK, has written a paper detailing evidence suggesting that the drug had been developed before Grünenthal secured a patent in 1954.

The company has always maintained that thalidomide was created by chance in 1953 by scientists who had tried to create an antihistamine but ended up with a tranquilliser.

Johnson suspects that it was actually first produced as a possible antidote to nerve toxins such as sarin, which was developed by Otto Ambros, a Nazi scientist who joined Grünenthal after the war.

"It is now appearing increasingly likely that thalidomide was the last war crime of the Nazis," said Johnson.

One document unearthed by the Thalidomide Trust shows that Grünenthal apparently purchased the trade name of the drug - Contergan - and therefore probably the substance itself, from a French firm, Rhône-Poulenc, which was under Nazi control during the war years.

A confidential letter sent from Astra, which held the Swedish licence to distribute thalidomide, to its Norwegian subsidiary in 1958 states: "Unfortunately we can't use the name Contergan in the Scandinavian countries, since Grünenthal obtained the name exclusively for the German market through an agreement with Rhône-Poulenc."

From 1942 onwards Rhône-Poulenc registered 14 similar drugs, all ending with the same "ergan" suffix, a characteristic unique to the firm. Many of the drugs shared properties with thalidomide, such as affecting the nervous system.

"Not only is the name typical of the Rhône-Poulenc brand names of the 1940s; the action of thalidomide also belongs among this range of products," said Johnson in his report.

Meanwhile, the author of a forthcoming book on Nazi scientists claims to have a copy of a document written in November 1944 by a director of IG Farben, the German pharmaceutical firm, which refers to the development of a substance, the chemical formula of which matches thalidomide.

Carlos De Napoli, an Argentinian who has published books on the activities of the Nazis who fled to South America after the war, claims his book, Hitler's Laboratories, will show that the drug has its origins in the Nazi death camps.

IG Farben, whose bosses, including Ambros, were convicted of war crimes such as slavery and mass murder, ran the synthetic rubber and petrol processing plant at Auschwitz-Monowitz, which drew its labour from extermination camps.

De Napoli said the memo was sent on November 13, 1944 by Fritz ter Meer, an IG Farben executive, to Karl Brandt, an SS general who was Hitler's personal physician and head of his euthanasia programme.

The report, in which the drug is referred to simply by a four-digit number - 4589 - states it has been tested and is ready for use. De Napoli says he discovered the document in the IG Farben archive in 1978 but realised only recently the significance of the formula it contained. "There is absolutely no doubt of the Nazi development of and experimentation with thalidomide in the world war two camps," he said.

Johnson said the 1954 patent for thalidomide implied that it had already been tested on humans, even though trials on people did not officially take place until later. Grünenthal subsequently said it had "lost" much of the testing paperwork.

Johnson concluded in his report: "The patents suggest that thalidomide was probably one of a number of products developed at Dyhernfurth [a chemical laboratory] or Auschwitz-Monowitz under the leadership of Otto Ambros in the course of nerve gas research."

Grünenthal said: "To our knowledge there was no collaboration between Grünenthal and Rhône-Poulenc for the development of Contergan/thalido-mide. Three Grünenthal employees discovered thalidomide and Grünenthal is the sole inventor on the patent."

Sanofi-Aventis, which took over Rhône-Poulenc, said it was searching its archives.

Experiments on prisoners

Grünenthal was founded in 1946 by the soap manufacturers Alfred and Herman Wirtz, twins who were both former members of the Nazi party.

Their chief scientist was Dr Heinrich Mückter, a fledgling pharmacologist who had carried out wartime experiments on Polish prisoners to find a cure for typhus. He caused the death of hundreds in the process.

According to Grünenthal, Mückter was one of those responsible for inventing thalidomide.

Otto Ambros was the most qualified scientist with Nazi links to work for Grünenthal. His knowledge was used by the Nazis to develop deadly nerve toxins such as sarin. He was sentenced to eight years at the Nuremberg trials.