Leading contender: Rory Bremner is tipped to take over on Channel 4's longest-running show

Comedian Rory Bremner is being lined up to take over from Des O'Connor as the new presenter of Countdown.

But the future of the show has been thrown into confusion amid a huge question mark over Carol Vorderman's continued presence.

Her contract is up for renewal and insiders say she and Channel 4 bosses are at odds over her new deal, sparking fears she will quit the quiz.

Vorderman has been on the show since it started in 1982, but the broadcaster is trying to slash costs on the programme, including what it pays talent.

While there is increased uncertainty about her role on Channel 4's longest-running show, Bremner has become the leading contender to replace 76-year-old O'Connor.

Channel 4 is understood to have made 'discreet enquiries' about award-winning comedian Bremner's availability in the coming months.

He is the now favourite ahead of presenters such as Aled Jones, Michael Aspel and Gyles Brandreth.

Bremner, whose selection would be seem a surprise booking, is one of the most enduring faces on Channel 4 in recent years.

Sources close to the impressionist have claimed if he was up for the challenge he would be able to fit the show around his existing commitments.

They add that Richard Whiteley, presenter of the show for over 20 years until his death in 2005, was a massive fan of the comedian.

Aled Jones, who shot to fame as the young singer of Walking In The Air - the theme song of animated Christmas favourite The Snowman - has now launched a career as a TV presenter of shows including BBC1's Songs of Praise.

Aspel and Brandreth, who has appeared in Countdown's Dictionary Corner, have both in previous years been linked with the job.

Uncertain future: Carol Vorderman, hitherto a Countdown fixture, with outgoing presenter Des O'Connor

Granada, which owns Countdown producer Yorkshire Television, is tightening budgets amid the advertising recession.

This has sparked problems as it has coincided with the renewal of Vorderman's deal.

Earlier this week O'Connor quit Countdown after less than two years, claiming he misses the excitement of his one-man concerts.

He will step down as host of the hit show in November, having joined it in January last year.

His relatively short stay comes after Des Lynam quit after only 18 months as Countdown host.

A Channel 4 spokesman said: 'A replacement for Des will be announced in due course.'