The investigation into the secret cash donations accepted by the former German Chancellor, Helmut Kohl, for his Christian Democrat Union (CDU) party dates back to 1995.

Back then public prosecutors in Augsburg in southern Germany started looking into a DM1m ($516,000) cash donation made to the CDU by an arms dealer, Karlheinz Schreiber, in 1991.

But the issue was left simmering in the background until the Social Democrats revived it in October 1999, when they mounted their own inquiry into allegations that the donation was linked to the sale to Saudi Arabia of tank components.

They also looked into suspicions that the sale of the East German oil refinery Leuna to the French oil company Elf in the early 1990s was accompanied by bribes to German politicians.

Arrest warrant

The scandal started gathering strength at the beginning of November when the Augsburg prosecutor issued an arrest warrant for Mr Kohl's former party treasurer, Walther Leisler Kiep.

He was charged with tax evasion on the basis that he intercepted Mr Schreiber's donation and used it for personal ends.

Mr Kiep quickly turned himself in to the authorities, denying the charges. He said he placed the donation in a trustee account held on behalf of the CDU and was later released on bail.

Mr Kohl called for a quick clarification of Kiep affair, insisting he knew nothing about the 1991 donation.

"I don't know anything about the matter," he said. "The political leadership of the party also knew nothing about it then."

A couple of weeks later, Mr Kohl also denied he had accepted bribes to allow the export of tanks to Saudi Arabia.

Scandal grows

But his denials failed to stop speculation about his involvement, leading him to make a dramatic appeal in parliament on 24 November for his name to be cleared by Christmas.

Only weeks earlier, Germany's elder statesman had been standing beside the former US and Soviet leaders George Bush and Mikhail Gorbachev, celebrating the 10th anniversary of the fall of the Berlin Wall and being feted as a hero.

The scandal continued to grow, with the former CDU campaign manager, Heiner Geissler, admitting the party had maintained secret accounts to funnel money to local party chiefs.

By 30 November, Mr Kohl was forced to admit to using a system of secret accounts to receive campaign contributions. But he insisted he did not accept bribes.

Any hopes he may had had of quashing the scandal were dashed just days later when the German parliament voted unanimously to open a full-scale investigation into the campaign funding scandal.

It was at this time that the Bonn prosecutor began to consider whether to open a full criminal investigation into Mr Kohl.

The former chancellor also came under pressure from his own party, with Christian Democrat leaders grilling him for six hours on 6 December for details of secret bank accounts.

Kohl's admission

But it was not until mid-December that Mr Kohl finally admitted accepting cash donations worth up to two million marks to help the party in the former Communist states in eastern Germany.

In his first detailed interview on the scandal, he said he had made mistakes but said he was never corrupt. But he refused to name the donors.

His admission failed to silence his critics. On 20 December the Justice Minister, Herta Daeubler-Gmelin, said Mr Kohl knowingly broke the law for years while in office.

Five days later, Chancellor Gerhard Schroeder attacked his predecessor over the scandal, saying Mr Kohl had behaved with contempt for the law.

The CDU, facing possibly the biggest scandal in its history, prepared for the worst, making provisions of DM7.3m ($3.8m) to cover possible fines under German party funding rules.

By 2 January, the scandal started to engulf Mr Kohl's successor as CDU leader, Wolfgang Schaeuble. Leading coalition politicians accused him of knowing about an illicit DM1.1m mark cash transfer from the CDU parliamentary group to party headquarters in 1997.

The following day, Bonn prosecutors launched their criminal probe. If Mr Kohl is charged and found guilty, he could face a big fine or a jail sentence.

On 18 January, Mr Kohl resigned as honorary chairman of the CDU, bowing to increasing pressure within the party.

However, he still rejected renewed calls to identify the sources of the cash donations which sparked the scandal.

Schaeuble in the frame

Wolfgang Schaeuble was one of Germany's most respected politicians who despite his closeness to Helmut Kohl, promised to get to the bottom of the finance scandal and ensure a full party investigation.

But on 10 January he admitted on German television that he had met the businessman at the centre of the scandal, Karlheinz Schreiber, at a CDU fundraising event in 1994 and had accepted a 100,000 deutschmark cash donation from him.

The party leader faced growing pressure to resign though he insisted he had done nothing wrong.

Four days later the Hesse branch of the CDU admitted having operated a slush fund worth millions of marks in secret Swiss bank accounts and having falsely presented the proceeds as bequests from deceased Jewish sympathisers.

The party's leader in Hesse, former interior minister Manfred Kanther was forced to resign. Further admissions from Hesse followed in February, with state premier Roland Koch revealing he lied to cover up his use of Swiss bank accounts as campaign funds.

On 15 February Parliament fined the CDU a record $21m for the irregularities. Unrest grew in the parliamentary party, in particular over Mr Schaeuble's account of the Schreiber gift.

The following day the party leader announced that he would not be standing for re-election.