Michael Jackson has gone to the US to run USA Entertainment

While remaining guarded about specific programming plans for the future, Mr Thompson suggested he would like to see more big budget dramas such as the �10m epic Antartic adventure Shackleton and David Starkey's The Six Wives Of Henry VIII.

"This is a moment in television history in which big bold programmes really punch through. I think that would really strengthen the schedule," he said.

"It's absolutely the case that I am completely focused. The reason I have taken this job is that it's a great job.

"Channel 4 is a beacon of creativity, innovation and independence and I am very proud to have been asked to lead it."

Channel 4's previous chief executive, Michael Jackson, had announced he was leaving as long ago as July.

But Channel 4 chairman Vanni Treves said the board had been determined to get the best candidate regardless of timescale.

'Nothing ruled out'

Critics of the appointment believe Mr Thompson will use the job as a springboard to eventually succeed Greg Dyke as director general of the BBC.

But Mr Thompson said while he did not want to rule anything out, he hoped to be at Channel 4 for years to come.

He will be charged with the job of steering Channel 4 through a difficult time for the whole industry as advertising revenues fall and digital costs rise.

He said he would miss the BBC and wished his colleagues well, but admitted he was an "admirer" of Channel 4's "independence and diversity".

I personally just don't believe that Channel 4's independence, it's commitment to real creative innovation and diversity would survive if the channel was privatised

Mark Thompson Chief Executive Channel 4

He praised shows like So Graham Norton and Big Brother, which he described as a "really outstanding programme and an example of Channel 4 taking big risks".

But on Richard and Judy's new offering, he said: "I think they are great broadcasters - it's early days."

Mr Thompson said he supported the channel's decision to screen the controversial Brass Eye paedophile spoof documentary, for which they were ordered to broadcast an apology to viewers.

He did not think his background in public service broadcasting, would be a handicap to his new role as he had been involved in running operations involving budgets close to �1bn.

He said he was against privatisation of the network. "I personally just don't believe that Channel 4's independence, it's commitment to real creative innovation and diversity would survive if the channel was privatised."

Channel 5's Dawn Airey: Ruled herself out

The married father-of-three joined the BBC in 1979 as a production trainee, rising to editorships of Panorama and the Nine O'Clock News.

He was director of national and regional broadcasting before his appointment as director of television.

In the past few years Channel 4 has launched Film Four and E4 for satellite, cable and digital users under the leadership of Mr Jackson.

He left for New York in October to start his new job as president and chief executive officer of USA Entertainment.

Various names were in the frame for the chief executive position, including Channel 5 head Dawn Airey and Endemol Entertainment's Peter Bazalgette.

But both ruled themselves out of the running by vowing to stay in their current jobs.

Mr Treves said the board had made their choice from a set of 10 shortlisted candidates from around the world.

Mr Dyke has asked Sophie Turner Laing, controller of programme aquisitions, to be the BBC's acting director of TV until a new director is appointed.