* To step down by year end after mutual decision
* Bulford to take over in the interim, if needed
(Adds details, quotes)
By Kate Holton
LONDON, Sept 16 (Reuters) - Channel 4, home to Big Brother and hard-hitting documentaries, is looking for a new chief executive after Andy Duncan said he would step down from one of the most high-profile jobs in British broadcasting.
Duncan said he had mutually agreed to leave before the end of the year, following five years in the job marked by a collapse in advertising revenues, attempts to find a commercial partner and an international race row.
The announcement means two of Britain's biggest broadcasters are in a state of management upheaval as rival group ITV nears an announcement on its new chief executive. Channel 4's Chairman Luke Johnson is also due to step down this year.
Channel 4 said Duncan would be replaced by finance director Anne Bulford on an interim basis if the company has not found a successor by the time he leaves.
Executives likely to be linked to the job are Kevin Lygo, head of content, ITV's director of content, Peter Fincham, Jana Bennett of the BBC and former communications minister Stephen Carter.
Channel 4 is publicly owned but commercially funded and was initially known for innovative and edgy programming. But it has in recent years become more closely tied to the reality programme Big Brother.
Initially drawing in around 10 million viewers after it launched in 2000, the show is set to finish in 2010 after losing its appeal.
It also caused Duncan his biggest headache, leaving him to handle the fallout after contestant Jade Goody faced accusations of racist bullying of another housemate, Shilpa Shetty, prompting tens of thousands of complaints and dominating the headlines for weeks.
Duncan, who also oversaw the group as it launched content online and on digital platforms, said he had decided to step down after coping with the dramatic structural change and unprecedented downturn better than most.
"In my remaining months I intend to see through important further steps towards securing the best possible future for this organisation, including... a number of exciting commercial partnerships currently under discussion," he said.
In his last year, Duncan had led the push to see Channel 4 partner or merge with another broadcaster to help it adapt to the new, tougher environment.
It has held lengthy talks about a partnership with the commercial arm of the BBC but nothing has been announced and industry insiders suggest any deal will be watered down since the request was made.
"Channel 4 is facing a further period of change, with a fresh regulatory cycle looming and with the cancellation of Big Brother signalling the most significant creative renewal in our history," he said.
"We have mutually agreed that this feels like the appropriate moment for me to hand on the baton to someone else and to move on to a fresh challenge after more than five years at the helm." (Reporting by Kate Holton; editing by John Bowker and Mike Nesbit)