Lord Birt, a former director general of the BBC, has warned that the corporation would be forced to make deep cuts if Scotland votes for independence, losing up to a quarter of its current spending.

He said the BBC would have to make "fundamental" changes to its programming and operations after a yes vote, while Scottish viewers would lose automatic access to all the corporation's TV and radio output.

Birt, writing for the Guardian, said the 15% spending cuts already forced on the BBC by the Westminster government would be greatly worsened after a yes vote, since it would then lose another 10% of its funding – the £320m currently paid each year by Scottish licence fee payers.

The former director general, now a crossbench peer, predicted the BBC would reject proposals by Alex Salmond's government for a close working relationship with a new publicly owned Scottish Broadcasting Service (SBS). It would sell its shows to the highest bidder in Scotland, such as STV, partly because it was becoming so strapped for cash.

"The bold assertion in the Scottish government's white paper that a new Scottish public service broadcaster will work with the BBC in a programme-swapping joint venture is make believe," Birt states. "One way or another, after independence, Scottish viewers would have to pay to receive BBC services."

The future of the BBC – which stages a major live debate next Monday on independence between Salmond and the pro-UK campaign leader, Alistair Darling, remains a significant concern for Scottish voters, a substantial majority of whom want the corporation to remain serving Scotland if there was a yes vote.

The Scottish social attitudes survey in June said 61% of voters wanted to keep all BBC's services intact and did not want a separate Scottish broadcaster, with 25% wanting both the BBC and a new Scottish service; and 11% wanting the BBC to be replaced in Scotland.

Salmond's government has proposed that a future SBS would take over all the BBC's assets and staff in Scotland, where BBC Scotland currently has a £205m budget – about £115m less than collected from the licence fee. Partly funded too by a £13m share of BBC Worldwide's profits and the £12m Scottish ministers give Gaelic digital channel BBC Alba, the SBS would have a £345m budget to run its own TV, digital and radio channels – a tenth of overall BBC spending.

The SBS would form a joint venture agreement with the BBC where it would continue supplying the corporation with the same amount of programmes from Scotland, in return for BBC services continuing as before, Scottish ministers argue.

The Scottish government's white paper in November stated: "Current programming like EastEnders, Doctor Who, and Strictly Come Dancing and channels like CBeebies, will still be available in Scotland. The SBS will continue to co-commission, co-produce and co-operate with the BBC network."

Birt retorted that this was highly unlikely to happen: "The BBC is, thankfully, independent of government – so whatever is asserted wishfully in the white paper, the BBC will have no alternative whatsoever but to act in the interests of its licence payers, and to seek the best possible commercial terms for the sale of its programmes in Scotland, not least because of the aforementioned financial impoverishment it will just have suffered.

"And, of course, there may be commercial broadcasters in a new Scotland willing and able to pay more for the BBC's most successful programmes than an impecunious SBS."

The Department of Culture, Media and Sport has refused to respond to these proposals in any detail or publish its own assessment of the broadcasting industry in Scotland and the future of the BBC. But in June, Danny Alexander, the chief secretary to the Treasury, told the Guardian that ministers in London would negotiate with Scottish ministers about the BBC if there was a yes vote; opinion polls currently show a large but shrinking gap between yes and no support.

Alexander said: "I'm very sceptical about such proposals but clearly if Scotland votes yes and there are negotiations, these are things that they can put forward. I'm sure that [the Scottish government] would put them forward."

Senior industry figures in Scotland believe that after independence, the UK government and BBC would want to agree a close working relationship with a Scottish public broadcaster because the corporation was protective of its British status, and its wider interests.

One production executive said Birt was unsurprisingly defending the status quo. Even if the BBC sold its shows to STV, few Scottish viewers would mind as long as they got to see EastEnders or Strictly Come Dancing, in a broadcasting world with new entrants like Netflix and Amazon. "From a consumers point of view, if you're getting Sherlock, does it bother you if it's on the BBC?" they said.

Fiona Hyslop, the Scottish culture secretary, declined to comment on Birt's criticisms and his claims BBC programmes would be sold to the highest bidder in Scotland. Her spokeswoman repeated the position taken in the white paper, saying a joint venture between the BBC and SBS would "give continuity of supply to the BBC and continuity of programming to the SBS, such an arrangement is in the best interest of all concerned and will ensure that decisions about broadcasting in Scotland are made in Scotland".