Mr Allen has struggled with poor viewing and advertising figures

ITV has been suffering from record low viewing figures and falling advertising revenues, so the new holder of the top job at the firm will face a tough time trying to turn things around.

Yet the role remains one of the biggest jobs in UK broadcasting, and a number of individuals are expected to put themselves forward for it.

At present, the favourite to replace Mr Allen is thought to be Channel Four chief executive Andy Duncan.

Other hotly-tipped candidates include Stephen Carter, former chief executive of media regulator Ofcom, and Sky managing director of channels Dawn Airey.

Here are some more details on the three main candidates:

Andy Duncan is currently chief executive of Channel Four.

Mr Duncan is credited with helping the BBC enter the digital age

The 44-year-old was previously the BBC's director of marketing, communication and audiences.

After university, his career started in 1984 when he joined Anglo-Dutch consumer product giant Unilever, rising through its marketing unit.

In 2001, he joined the BBC as director of marketing and communication, with the audiences remit added two years later.

He is said to have helped successfully lead the BBC's transition to digital television.

In 2004, he took up the chief executive job at Channel Four.

Mr Carter, 42, stepped down from the top job at Ofcom last month after three years in the role.

Mr Carter is the favourite to succeed Mr Allen

Ofcom chairman Lord David Currie said Mr Carter had "performed outstandingly".

"His legacy is an effective and credible organisation which plays an important role in delivering greater choice, lower prices and greater innovation," said Lord Currie.

Before joining Ofcom in 2003, Mr Carter was chairman of cable company NTL.

Described as an industry heavyweight, he is favourite to replace Mr Allen.

Yet some media reports say ITV's rivals, such as the BBC and Sky, wish to block Mr Carter's appointment, claiming that his role at Ofcom has given him access to too much sensitive information about their business plans.

Mr Carter has made no comment on the top job at ITV and is currently on holiday.

Dawn Airey has been involved with a number of TV companies during her working life.

Ms Airey has worked for a number of television firms

Her career started in 1985 when she joined Central TV as a management trainee, rising in 1988 to controller of programme planning at the station.

In 1993, she became ITV's controller of network children's and daytime programmes. Just a year later, she switched to Channel Four, where she was appointed its new controller of arts and entertainment.

Then in 1996, she was appointed director of programmes for Channel Five before it began broadcasting in 1997.

She stayed with Channel Five until the end of 2002, rising to become chief executive.

Ms Airey then joined Sky in 2003, where she remains in the position of managing director, Sky Networks.