The BBC's director of television has refused to guarantee that BBC4 will stay on air beyond the next licence fee settlement following the decision to make sister channel BBC3 online only.

A former controller of BBC3, Danny Cohen admitted it was "painful" to close down the 11-year-old youth channel, after the BBC confirmed on Thursday that it would cease transmission in the autum of 2015, becoming an on-demand service available via the iPlayer.

However, Cohen said the BBC had no choice because of the 2010 licence fee settlement, which saw the corporation take on extra funding responsibilities such as the World Service.

Asked by Richard Bacon on BBC Radio 5 Live on Thursday afternoon if he could guarantee the future of BBC4, Cohen said: "The honest answer is no, I can't. We don't know for certain what will happen with BBC4 in the future.

"The reason we made this change for BBC3 is because we face a series of financial cuts the like of which the BBC has not had to cope with before.

"In an ideal world we would not be taking BBC3 online in 18 months time, we would probably do it in three or four years time.

"But taking on the World Service cost £245m to licence fee payers, we took that in from the government in the last licence fee settlement along with another set of commitments totalling £300m. It means we can't keep offering the same with less money.

"For BBC4, that means if future funding for the BBC comes under more threat then the likelihood is we would have to take more services along the same [online only] route [as BBC3]."

Cohen added: "By making the move we made today we know we can manage our funding through the licence fee period which ends in 2016/17. We will have to see what happens in the future with the licence fee whether we can keep BBC4 [as a TV channel]."

Cohen's comments will be seen in the context of the charter renewal and licence renewal negotiations with the government, which will be completed by they end of 2016.

They will be seen as a warning shot, across the bows of opinion makers and the government, that further cuts to its funding in the next licence fee deal with result in the loss of more services including the politicians' favourite, BBC4.

Cohen said the closure of the BBC3 TV channel was "quite painful to be honest. I don't regret it because I don't think we have made the wrong decision. We are doing it now rather than in three or four years time because of financial reasons."

He said the alternative to closing a channel was asking channel controllers and programme makers to make cuts of 20% to 25% of the budgets. "The impact on the quality of shows people love would be very substantial," he said.

"We had a choice whether to make one big bold move or cut budgets and affect quality across the board."

He admitted older viewers were overserved by the BBC but said the decision to move BBC3 rather than BBC4 online was taken because its audience was more likely to be able to adapt. "It was a strategic decision," he said.

Earlier on Thursday, the BBC's director general Tony Hall also explicitly linked the closure with the 2010 licence fee settlement, which cut BBC funding by 16% in real terms and led to former director general Mark Thompson's £700m Delivering Quality First cost-saving drive.

"We have to make some tough decisions and people keep saying to me salami slicing is not going to get to the position where we need to be under the licence fee," he told Radio 4's World at One.

"In truth we would not be rushing at this in quite the speed if it was not for the financial situation we find ourselves. We'd be taking longer to transfer an audience from a broadcast model to a new model, but the finances make this imperative."

Hall said BBC3 currently had a content budget "somewhere north of £50m" which would be cut to £30m when it goes online only.

He admitted that only 9% of BBC3 viewers currently watch it on the iPlayer but said he believed it would "increase quite rapidly".

He said money would be ploughed into BBC1 drama because its budget was "falling off in a way I am not satisfied with" and he was "not prepared to compromise on quality.

"It would be awful if the quality of what we do gradually goes down. To retreat from quality or distinctiveness would be dreadful".

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