German prosecutors have charged six former directors of telecoms firm Mannesmann, alleging illegal payments made during the firm's takeover by Britain's Vodafone in 2000.

The six have not yet been officially named, but Mannesmann's former chief executive Klaus Esser has already admitted being on the list.

According to media reports, the others include Josef Ackermann, chief executive of German finance powerhouse Deutsche Bank, and Klaus Zwickel, head of influential trade union IG Metall.

Vodafone's chief executive Sir Christopher Gent has been excluded from the investigation, according to a statement from the company.

"Vodafone would like to point out that Sir Christopher�s solicitor in Germany has received a formal letter from the Dusseldorf State Prosecutor�s Office... stating that proceedings against Sir Christopher had been dropped," it said.

The charges relate to a multi-million-dollar bonus package given to senior Mannesmann executives, after they had agreed to the �112bn ($179bn) merger.

The alleged payments were to "smooth over" the takeover, which was at first fiercely resisted by the German company.

Allegations denied

Mr Esser has suggested the charges were arbitrary and insisted he behaved properly.

"There is not the slightest suspicion of any kind of illegal behaviour on my part," he told Reuters news agency.

He received a 30m-euro (�20m) golden handshake as part of the deal.

German state prosecutors said they would not name the six people they had decided to charge.

Golden goodbyes

The prosecutors have spent the past two years investigating the sizeable bonuses received by former Mannesmann managers at the end of the lengthy takeover battle.

The deal took months of fraught negotiations and met with fierce opposition from Mannesmann staff and German politicians - both angered at the suggestion of a UK rival taking over one of Germany's best-known companies.

Prosecutors were looking into Mr Esser's decision to climb down from his bitter opposition to the deal.

They also said the huge sums paid to Mannesmann executives to secure the deal - some 107m euros - were against the interests of shareholders.