* Joint CEO Fitschen's contract to be extended to 2017
* Supervisory board to formalise decision in October
* Carbon tax fraud investigation not completed - prosecutor
FRANKFURT, Sept 11 (Reuters) - Deutsche Bank joint Chief Executive Juergen Fitschen's contract is set to be extended by two years, keeping the leadership at Germany's biggest lender in place until 2017.
Deutsche Bank said in a statement on Wednesday its supervisory board would formalise the proposal from a board sub-committee at a meeting on Oct. 29.
The move addresses concerns raised by investors at a shareholder meeting this year that Deutsche may relapse into the uncertainty over its leadership that plagued it as the era of previous CEO Josef Ackermann came to an end.
Under the proposal presented on Wednesday, the contracts of Fitschen, 65, and the bank's other CEO, Anshu Jain, 50, would continue until March 31, 2017, Deutsche Bank said.
Fitschen's existing contract expires after Deutsche's annual general meeting in May 2015.
Two people familiar with the supervisory board's thinking told Reuters of the plan earlier on Wednesday.
"That will nip in the bud any discussion over succession," one of the sources said. The other person said there was no sign of friction between the two chief executives.
"Jain is happy because he has in Fitschen someone who eases the burden and knows the culture of the bank in Germany very well. At the same time, Fitschen is not someone who can become a threat to Jain," the second person said.
Fitschen was important in representing the bank to the outside world, although Jain was already accepted as the bank's internal leader, the source said.
"It looks pretty certain that from 2017 only one man will be running the bank and that's Jain, provided there's not some new legal problem that crops up," the source said.
Fitschen himself is involved in a judicial investigation of 25 Deutsche employees suspected of tax evasion linked to tax credits and a scheme involving the trading of carbon permits.
Frankfurt prosecutor Guenter Wittig said on Wednesday that there was nothing new to report on the investigation.
"The investigation is not yet finished," he said.