The former Chancellor, who last week admitted running secret accounts for many years, refused to address the press yesterday. But Wolfgang Schauble, the party's new leader, said Mr Kohl assured them of his readiness to co-operate with the inquiry. Mr Schauble said the Christian Democrats would like to complete the investigation before the end of the year, but the independent accountant from Ernst & Young had been unsure if this was possible. The missing files include those of bank transactions from 1994 to 1996. Mr Kohl's unorthodox banking regime was introduced shortly after he became chancellor in 1982, Mr Schauble confirmed, and were wound up the day he left the party chairmanship last year.
As anger swells among the Christian Democrats, senior figures are urging that the party should come clean quickly. "The party is in a difficult position," Angela Merkel, a former Kohl protege and now General Secretary, told Bild Zeitung. "I believe it would be good if he did everything he could to uncover what happened."
At one Frankfurt bank alone, the party is reported to have kept 17 secret accounts. This is where Horst Weyrauch, the CDU's tax adviser, deposited anonymous donations over several years, and shunted the money about by withdrawing the entire contents and paying the cash into a new account. That left no paper trail, violation of the political funding law.
Mr Weyrauch had also made frequent trips to Switzerland, sometimes twice a week. He told prosecutors he could not remember the purpose of these visits. At least one secret account, which at one point contained DM500,000, has been traced to a Zurich bank. Mr Schauble said yesterday he was unaware of a link between his party and Swiss accounts.
As the investigation drags on behind closed doors, pressure is mounting on Mr Kohl within his party to stand down as an MP. That would avoid a lengthy political battle, should prosecutors in Bonn decide this week to open criminal investigations.
Mr Kohl has admitted publicly that he may have broken party financing laws, but has defended the secret funds as part of his highly personalised style of running the party - suggesting he used the hidden contributions to build loyalty among favoured party officials.
The former Chancellor enjoys parliamentary immunity, which can be lifted only with the agreement of the Bundestag. Parliament has launched an inquiry into his chancellorship.