Newly discovered documents from Hitler's Germany prove that the computer company IBM directly supplied the Nazis with technology which was used to help transport millions of people to their deaths in the concentration camps at Auschwitz and Treblinka, a controversial Holocaust expert claims in a new edition of book published later this week.

Edwin Black, whose book IBM and the Holocaust was published in hardback last year, says new evidence set out in the paperback version shows that executives at the firm's New York headquarters directly controlled a Polish subsidiary which leased punch-card machines used to "calculate exactly how many Jews should be emptied out of the ghettos each day" and to transport them efficiently on railways leading to the camps.

When the Nazis invaded Poland, Black wrote in the Jerusalem Post, "IBM New York established a special new subsidiary called Watson Business Machines," after its then- president, Thomas Watson. "IBM's new Polish company's sole purpose was to service the Nazi occupation during the rape of Poland." Watson Busi ness Machines even operated a punch-card printing shop over the street from the Warsaw Ghetto, the paperback claims.

In the earlier edition of Black's book, the connection between the US headquarters of IBM and its European operations was more sketchy, tracing the supply of machines to a German subsidiary that had been seized by the Hitler government.

The paperback provides the first evidence that the company's dealings with the Nazis were controlled from its New York headquarters throughout the second world war.

Mr Black quotes Leon Krzemieniecki, the last surviving per son involved in the Polish administration of the rail transportation to Auschwitz and Treblinka, as saying that he "knew they were not German machines... The labels were in English...

"The person maintaining and repairing the machines spread the diagrams out sometimes. The language of the diagrams of those machines was only in English."

During the war, Mr Black says, a senior IBM representative from New York travelled to Berlin to meet a Czech IBM executive and arrange for the lease payments on the Hollerith card machines to be transmitted via Switzerland to New York.

To the book says the Czech was in a position to send income from the machines leased in Poland through Geneva to IBM in New York.

Robert Wolfe, a researcher on Mr Black's team who was formerly in charge of Nazi documents in the US national archives, said the new details would silence detractors.

"The word has gotten out, and a lot of people still alive are supplying information that they didn't have the context to understand before," he told Reuters. "For those who have complained the proof is not there, this leaves little room for deniability."

The first edition of IBM and the Holocaust prompted a group of death-camp survivors to launch a legal action against IBM, but it was dropped in case it might delay other compensation payments to the victims of the Nazi regime.

Much of compensation process has now been completed, raising the possibility that the paperback may revive the legal proceedings.

"This negates all the excuses," Malcolm Hoenlein, a vice-president of the conference of presidents of major Jewish organisations, said.

"IBM has to look at what its role should be in light of these revelations."

The company, now based in Armonk in upper New York state, has not denied the role of its subsidiaries in aiding the Nazis' management of the Holocaust, preferring to suggest that it should not be held responsible for the actions of companies of which the Third Reich had seized control.

It is not entirely clear that IBM's New York executives knew the ultimate use to which their machines were being put.

But Mr Black cites numerous examples of stories in US newspapers at the time which he says should have left IBM in no doubt about the nature of the Nazis' murderous activities in Poland.

The new book's claim that "IBM recovered all its Polish profits and machines" after the German surrender is likely to be among the most incendiary of its allegations.

"We have seen no proof of that," IBM told the Guardian yesterday. "Facts which had been known for many years were used as the basis of allegations in the first book, and they seem to be used in similar fashion in the paperback. We're not convinced that there are any new findings here."