Some of the biggest names in British TV have joined the battle to save BBC3.
Actors including Daniel Radcliffe, Imelda Staunton, Olivia Colman, James Nesbitt and Maxine Peake are among more than 750 people, including talent from in front and behind the screen, to condemn the decision to move BBC3 online.
Game Of Thrones star Lena Headey, Poldark's Aidan Turner and Richard E Grant plus comedians Jack Whitehall, Steve Coogan, Al Murray and Rob Brydon are among a host of stars who have signed an open letter to Rona Fairhead, chairman of the BBC Trust, and BBC director-general Tony Hall.
They are calling for the decision to axe the channel as part of a cost-cutting drive to be reversed.
The corporation announced last year that the channel, which was home to hits like Gavin And Stacey, would go online only.
The letter, which will be delivered today, says: "Disastrously the closure and move online will remove at a stroke a vitally important outlet for new talent and innovative ideas, where some of the most successful and influential names currently working in British television were given their first chance."
Writers including Jimmy McGovern, Andrew Davies , Alan Bleasdale, William Boyd and Hanif Kureishi have also signed up.
TV executives and agents are also among those who have signed the letter.
They claim that moving the channel online and cutting its budget will alienate a key audience of young viewers and risk the future of the BBC, warning: "To disenfranchise the young viewer and pull back from the funding of new ideas and new talent risks endangering the engagement of future generations with the BBC."
The letter adds: "Either the BBC can continue to cater predominantly for an increasingly elderly audience or it can take the lead and safeguard its position as a beloved and relevant public broadcaster by investing in the talent and the audiences who are the building blocks of the future."
Campaigners delivered a petition in February which was signed by 271,222 people calling on the BBC not to make it online-only as part of cost savings.
This petition was delivered to the BBC Trust, which has yet to approve the plan.
A BBC Trust spokesman said: "The trust has been robustly assessing the BBC's proposals, informed by an assessment of the market impact by Ofcom, and listening to the view of audiences and the rest of the industry.
"The next stage in the process will be to publish a provisional decision on which there will be a further opportunity for people to comment, and we hope to do that in the coming weeks."
A BBC spokesman said: "We're pleased so many people feel strongly about the BBC's services, but the reality of having the licence fee frozen since 2010 means tough decisions have to be made.
"We also agree this is a tipping point for British broadcasting because young people want great content that's relevant to them at a time of their choosing irrespective of which screen it's on - and that's why rather than simply closing BBC3 we're proposing reinventing it online.
"We will still make great drama, comedy and documentaries but also embrace change and be something young people want, something that gives them a voice and gives a platform to future generations of on and off-screen talent."