Their methods had echoes of the Gestapo: kidnapping at night by state officials who offered no evidence of identity. Recently declassified secret documents reveal how at the end of the second world war an elite British unit abducted hundreds of German scientists and technicians and put them to work at government ministries and private firms in the UK.

The programme was designed to loot the defeated country's intellectual assets, impeding its ability to compete while giving a boost to British business.

In a related programme, German businessmen are alleged to have been forced to travel to post-war Britain to be questioned by their commercial rivals, and were interned if they refused to reveal trade secrets.

The economic warfare programmes are detailed in batches of Foreign Office files, marked "Top Secret", many of which lay unseen at the National Archives at Kew until discovered by the Guardian.

The files detail the way in which the scramble to uncover the Nazis' military secrets during the dying days of the conflict in Europe, to assist the continuing war effort in the Far East, turned rapidly to an early cold war campaign to prevent Germany's scientific and industrial assets falling into Soviet hands. This, in turn, offered the British government an opportunity to exploit the scientific and technical know-how of the defeated nation, with scientists being regarded as a form of human booty who could help give the UK an economic and commercial edge

While it has long been known that German scientists and technicians worked in the US and Britain after the war, it has generally been assumed they were all volunteers, lured by the promise of good pay and accommodation. However, the declassified papers make clear that for more than two years after the cessation of hostilities the British authorities were subjecting them to a programme of "enforced evacuation".

One memo found at Kew, written in August 1946 by a senior civil servant working with the British military government in northern Germany, makes clear how this programme worked. "Usually an NCO arrives without notice at the house or office of the German and warns that he will be required. He does not give him any details of the reasons, nor does he present his credentials. Some time later the German is seized (often in the middle of the night) and removed under guard.

"This procedure savours very much of the Gestapo methods and, quite apart from causing great and unnecessary inconvenience to the individual and to the industry employing him, it is bound to create feelings of alarm and insecurity.

"I have not been able to get to the bottom of the matter, but there appear to be two bodies which carry out these kidnappings."

He was right. The records show that abductions in the British-controlled zone of post-war Germany were carried out on the orders of an organisation called the British Intelligence Objectives Sub-Committee, or Bios. This committee was answerable to the cabinet and made up of representatives of the armed forces and Whitehall departments, including the Board of Trade and Ministry of Supply, as well as MI16 - the War Office's department of scientific intelligence.

The other organisation was the Field Information Agency (Technical), or Fiat, which had been established during the war as a joint Anglo-American military intelligence unit, and which earmarked scientists for "enforced evacuation" from the US and French zones, and Berlin.

The papers even record how 50 scientists were rounded up from their homes in Magdeburg in the Russian zone in June 1945, with many complaining over the loss of their homes, jobs and pensions.

Bios and Fiat both had offices in the same anonymous-looking Victorian town-house off Baker Street in London, from where investigators would be dispatched to search among the rubble of the shattered nation. While many factories were being dismantled, as part of a post-war plan to limit Germany's industrial capacity, the investigators would look for state-of-the-art machinery to be shipped back to Britain, research papers to be taken away and patents to be appropriated. These teams would often include representatives of firms such as ICI and Courtaulds, and others from the shipbuilding, steel or aerospace industries, usually wearing British army officers' uniforms. As well as deciding which equipment and documentation to take, they also identified scientists and technicians to be removed.

The legality was never questioned: the British military government's Proclamation No2 included a catch-all clause which said Germany would "provide such transport, plant, equipment and materials of all kinds, labour, personnel, and specialist and other services, for use in Germany or elsewhere, as the allied representatives may direct". Bios and Fiat also took advantage of post-war legal disagreements over what could be taken as reparations - which had been carefully negotiated by the allies - and what could be taken as "booty" - military material which the victors were entitled to seize from the battlefield. After six years of total war, the British took the view that anything of scientific or industrial importance had a military potential, and that the whole of Germany had become a battlefield.

Responsibility for seizing the scientists fell to a unique British army unit known as T-Force. Formed shortly after D Day, this lightly armed and highly-mobile force had raced ahead of allied troops at the end of the war, seizing objects which had a scientific or intelligence value before they could be sabotaged by retreating Germans, or captured by the Soviet Union.

After the war some officers and men from T-Force were formed into the Enemy Personnel Exploitation Section, which would escort the Bios and Fiat investigators and then take away the scientists and technicians wanted for interrogation.

Many of the detainees had indeed been involved in armaments work. The papers show that among those most sought after were men with expertise in underwater acoustics, infrared technology, electron microscopes, munitions, optical glass and aircraft engine design. Other target lists at Kew reveal a determination to trace technicians with knowledge of a "method of causing temporary blindness by ultra violet rays", the manufacture of Sarin gas, and "physiological trials of chemical warfare gases" - which had been conducted on concentration camp inmates.

Also among the Bios teams, however, were British industrialists eager to learn more about anything from the coal mining to comb making, and from latest German printing technology to the secrets of leading perfume manufacturers.

In November 1946 the New Statesman reported that three members of a six-strong Bios team, which included representatives of Pears Soap, Max Factor and Yardley, had called at the home of an elderly woman whose family firm manufactured 4711 eau-de-cologne, a famous brand, and attempted to bully her into handing over the recipe. When she was taken ill the team threatened to call a prison van to take her to a prison hospital. Next day they telephoned to try again.

As a young civil servant, Julia Draper was the only civilian and the only woman attached to T-Force, where she would help to track down German scientists. Now aged 86, she recalls at her home in London that Bios investigators were as much concerned with capturing the intellectual property of British industry's German rivals as they were with learning more about the Nazis' military secrets.

"Many of the requests came from the War Office, but there were also requests from businesses like ICI and the other major industrial firms," she says. "Some of these scientists were remarkably important people in their field, and there was a lot we could learn from them."

She recalls scientists being detained and sent to Britain against their will. "There were things of that nature. T-Force was a very, very strange organisation to be in."

Some of the Germans would undoubtedly have volunteered to help, but others were clearly compelled. The files show some were imprisoned in an Anglo-American internment camp near Frankfurt, while many were taken to internment camps in Britain. After interrogation, which could last months, they were either returned to Germany or put to work with government ministries or British firms.

It is unclear exactly how many men fell prey to this programme. In July 1946 military government officials told the Foreign Office they estimated there were 1,500 scientists who should forcibly be evacuated, 500 of them in the British zone. "The proposed long-term policy is ... to remove as soon as possible from Germany, whether they are willing to go or not." Minutes of a Bios meeting three months later quote one official as saying the organisation could not deal with more than 600. The civil servant who complained of the "kidnappings" and "Gestapo methods" wrote that he knew of seven scientists from one IG Farben chemical plant who had been abducted in the previous two months.

Those who were put to work in Britain were paid, with Bios agreeing that each scientist would receive 15 shillings a week to cover expenses. Initially, however, no provision was made for wives and children left behind.

In May 1946 the British military government urged Bios to make payments to dependants, as "cases of extreme hardship have previously occurred through Germans being removed to the UK for interrogation". Fiat was also concerned about this, but wanted the government to provide the funds. "Several familes ... are completely destitute," Fiat warned, adding that "this is likely to have very unfavourable effect on cooperation of other German scientists and technicians".

By October of that year some US army officers were refusing to allow T-Force to remove scientists from the American zone unless they provided payments in advance. The following month came the British response: each wife and child would be provided with "heavy workers' rations", and each family would receive 250kg of coal a month.

Scientists were not the sole targets. The papers disclose brief details about Operation Bottleneck, which aimed to extract business information. In January 1947 Erich Klabunde, head of the German journalists' union, complained about how this was being achieved. A British official in Hamburg reported to headquarters that Klabunde told a public meeting: "An English manufacturer would name his German counterpart and competitor and 'invite' him to England (whether the man comes voluntarily or not is questionable). They then discuss business and the German is gently persuaded to reveal secrets of his trade. When he refuses, he is kept in polite internment until he gets so tired of not being allowed to return to his family that he tells the Englishman what he wants to know. Thus for about £6 a day the English businessman gains the deepest secrets of Germany's economic life."

The rationale for this had been set out by Herbert Morrison, lord president of the council, who told the prime minister, Clement Attlee: "It is most important at this formative stage to start shaping the German economy in the way which will best assist our own economic plans and will run the least risk of it developing into an unnecessarily awkward competitor."

The British were not alone in trying to secure commercial advantage from Germany's scientists: countless numbers had also been snatched by the Russians. The French used a different approach, luring skilled workers with lucrative contracts, and the Americans offered US citizenship to those they wanted most, including Wernher von Braun, who had headed the V2 rocket programme and went on to be chief architect of the Saturn V rocket which propelled the US to the moon.

While the Foreign Office warned against bringing scientists with "politically undesirable" backgrounds to the UK, the papers show little evidence of industry being concerned about the employment of Nazis.

By early 1947 the Foreign Office, exasperated at the way in which the looting of German industry, by all four occupying powers, was impeding the country's reconstruction, secured an agreement that it would cease. Accordingly, the British were expected to stop abducting scientists, and the military government sent a telegram to T-Force ordering that all "industrial and technical investigations will be terminated by 30 June 1947".

There was no intention of allowing these scientists to do as they pleased, however, as some may have chosen to work for the Soviets. In April the Ministry of Defence drew up a list of 290 scientists to be traced urgently. This formed the basis of a so-called denial list "against whom denial measures should be taken as a matter of urgency".

Allowing German arms experts to settle elsewhere in Europe would be equally inadvisable, a Foreign Office discussion paper noted. "It has hitherto been an objective of British policy to encourage the smaller powers, particularly in Europe, to equip their forces with aircraft and weapons of British design. If these countries were to obtain technical reinforcement by recruitment of German research workers and designers they would be less likely ... to rely upon armaments of British design."

From now on, however, German scientists were to be given employment contracts - which included a clause forbidding them ever to talk about their experiences - and strongly encouraged, rather than coerced, into travelling to Britain. By the end of the summer, hundreds were employed across Britain.

While many British industries, particularly aerospace and armaments, wished to employ them, others were not sufficiently well organised to do so and there were too many scientists and too few jobs. The government sent a few to Canada and Australia, and then appears to have concluded that they should go anywhere - except Russia or Europe. It must have been in some desperation that Ernest Bevin, the foreign secretary, suggested to the cabinet defence committee: "Would it not, for example, be possible to carry out some fundamental research in Kenya?"

Beneficiaries

British industrialists were eager to learn as much as they could from Germany, from the mining of coal to the making of perfume. According to the National Archives, companies that employed German scientists and technicians immediately after the second world war included:

· ICI, the chemicals giant

· Courtaulds, the manufacturer of fabric, clothing, and artificial fibres

· Pears, the soap and cosmetics company

· Yardley, the maker of fragrances and toiletries

· Coal Oil Development, a company based in Swansea

· BSA Tools, the Birmingham machine toolmaker