BBC3 is now virtually certain to close as a broadcast channel in January next year after the BBC Trust today gave provisional approval to the plans.

The Corporation’s regulator said that the bid by BBC management to make the youth channel an online-only service offered “clear long-term potential” and would be “more distinctive than the existing BBC3 channel whose audience is currently falling”.

The report by the Trust said: “Those aged 16 to 34 are already far more likely than any other group to use online video services and the BBC is right to anticipate the need to service this audience in new ways”.

The decision will come as a blow to campaigners hoping to save BBC3 as a broadcast channel. These include Poldark's Aidan Turner, and scores of other actors including Broadchurch's Olivia Colman and Harry Potter star Daniel Radcliffe, who recently signed a letter opposing the closure.

There is now just a further 28 days more consultation with industry bodies and viewers before the decision is rubber-stamped – something Trust sources say is almost certain to happen.

The Trust did not offer many stringent conditions to the proposals as some campaigners had been hoping.

It did insist on what it called “a more carefully managed transition from broadcast TV to an online service, to raise awareness of the change” and called on BBC1 and BBC2 for “clearer commitments” to making programming that appeals to younger audiences.

The Trust also demanded that BBC1 and BBC2 formally commit to offer “space” to programming “where risks can be taken and new ideas of the sort that BBC3 has been successful in developing”.

However, those keen that the Trust insist on a budget boost for the online BBC3 had their hopes dashed. This means the new service will operate on an annual budget of £30m per year. Currently the channel runs on £55m.

The bid by Avalon and Hat Trick bosses Jon Thoday and Jimmy Mulville to buy BBC3 is barely addressed in today’s report, largely because their plans were not part of the BBCs’ management proposals, say sources.

However some of their concerns about the closure are addressed in a weighty 135-page document outlining the Trust's thinking.

While the BBC executive will be pleased with the decision, it did receive a knock back from the Trust which rejected its proposals to replace the BBC3 space on the Electonic Programme Guide with a BBC+1 catch-up channel.

The Trust said that the plans failed its public value test for a number of reasons. These include the adverse impact the channel would have on commercial rivals, the fact that the proposal was not distinctive enough and its belief that the new channel would have a limited impact on 16-to-34-year olds.

Today's interim decision about BBC3 had been delayed because the BBC Trust needed more time to conduct its public value test by canvassing the views of viewers and industry bodies. 

The report formally confirms that the plan is for BBC3 to stop broadcasting over the airwaves in January 2016.

Speaking at a briefing for journalists today, BBC Trust Chair Rona Fairhead said: “We know young audiences are already moving towards the online future, but we do recognise in the short term some of them will feel the immediate impact of the BBC3 proposals. We are therefore asking the BBC for commitments to ensure it uses the full range of its television services to better serve young people and others who make up BBC3’s audience.

"We all know in the future that many more people will watch online ... the BBC needs to adapt to that challenge to learn to make greater content online."

The BBC executive responded to the decision with the following statement: "We welcome the Trust's provisional conclusion, which is the next step in delivering our vision for a new BBC3. With a frozen licence fee and the BBC's income cut by 26% we have had to make some very difficult choices, however our plans will allow us to innovate with new ideas and new forms of content for younger audiences. We'll now consider the areas the Trust have asked us to address and respond in due course."