Pan-European broadcaster RTL is understood to have received expressions of interest in Channel Five from as many as a dozen potential buyers, including Daily Express owner Richard Desmond and Big Brother producer Endemol.

RTL is exploring a range of options for Five, including a sale or commercial partnership with the loss-making broadcaster, with a deal expected by the end of the year but with no deadline yet set.

It is not yet clear how many of the expressions of interest will yet turn into serious approaches, but it is understood that RTL has been contacted by companies outside the media industry.

Approaches are said to have been made by groups including US media company Time Warner, Endemol, ITV and BSkyB.

Desmond, who has appeared in the media frequently recently making it clear he has �1bn to spend on acquisitions, has also emerged as a potential bidder. Desmond owns newspapers including the Daily Express and OK! magazine as well as adult TV channels through subsidiary Portland.

There has also been rumours of interest from other US broadcasters as well as private equity companies.

In March MediaGuardian.co.uk revealed that the RTL chief executive, Gerhard Zeiler, had met Channel 4 chairman Terry Burns and chief executive David Abraham to discuss potential areas of commercial partnership, including a full merger.

Sources say that there is no urgency to the negotiations and that there is no first round deadline that has necessarily been reached. “There is no timeline to this, if someone was to emerge would they be listened to, of course,” said the source.

Several sources say that RTL is not considering any deal that includes Fremantle Media, which owns subsidiaries including TalkbackThames and makes shows including The X Factor.

One of the issues with buying Five, apart from it suffering against larger rivals and losing scale in the UK TV ad market, is onerous foreign programme deals such as a lifetime series commitment to contribute to the production of Home & Away.

In March RTL was forced to cut the value of Five by more than half, valuing it at �112m, after the broadcaster reported losses of �41m (�37m) last year.

In the past Zeiler has argued that Five is worth much more than its paper value because of the strategic role it plays in the wider market to a number of potential buyers. Reports have suggested Five could be worth well over double its book value and as much as �250m to the right party.

RTL made a �337m writedown in the value of Channel Five to �252m in its full-year results for 2008.

Sourdce: mediaguardian