Discovery Communications and BSkyB are poised to announce a £350m deal to acquire UK broadcaster Channel 5 from Richard Desmond’s Northern & Shell, according to Screen’s sister publication Broadcast.

Full details are not known, but Discovery is thought to have a 70% share of the deal with BSkyB taking the remaining 30% share, allowing it to add C5’s advertising inventory to its own sales operation.

The deal will mark a significant step for US media giant Discovery, which has been keen to ramp up both its international portfolio and its exposure to free-to-air broadcasting in key markets.

“We have a number of bids as expected, which we will evaluate with our advisors over the next few days,” said a C5 spokesperson. “Certainly no deal has been done.”

The joint Discovery and BSkyB bid has been the favourite since Broadcast revealed that around 20 parties were interested in submitting bids in March.

MTV-owner Viacom and Scandinavian media firm Modern Times Group were the dark horses, and there was also talk that Desmond could pull the sale process or look to float C5 if a deal was not agreed.

Desmond bought C5 from RTL in 2010 for £104m. While he was reportedly hoping to attract bids of closer to £600m, he will be happy to have tripled his money in less than four years.

The acquisition would be the most significant deal in the UK free-to-air market since the launch of C5 in 1997.

The deal, which will still be subject to regulatory sign-off, will likely have a massive impact on the channel’s programming budget, with some sources suggesting that it will be more than doubled.

Discovery declined to comment.