Mr Kohl, the Chancellor in 1991 when the German firm Thyssen exported 36 tanks to Saudi Arabia with government approval, described the charges as "evil". Prosecutors questioning the Christian Democrats' former national treasurer, Walther Leisler Kiep, suspect him of evading the payment of tax on the DM1m campaign donation to what was then the governing party.
Mr Kohl and other senior Christian Democrats say they know nothing of the alleged donation. The former chancellor maintains that he had already approved the sale of the tanks in 1990. But the newspaper Suddeutsche Zeitung claimed yesterday that the deal had been rejected in 1990 by the defence minister at the time, Gerhard Stoltenberg. According to the report, the sale went ahead a year later, about the time the campaign donation is alleged to have been paid.
Prosecutors believe the DM1m was paid by Karlheinz Schreiber, an arms dealer who is currently in Canada and is sought by Germany on tax evasion charges.