Lord Birt said if voters north of the border opted to separate from the UK, the BBC would lose a slice of its funding while the new public service broadcaster in Scotland would have to live within "modest means".
The establishment of a Scottish Broadcasting Service (SBS) is envisaged in the independence white paper, which goes on to state that this body would continue to supply the BBC with the same level of programming as BBC Scotland currently does, and in return viewers in an independent Scotland would have ''ongoing access to BBC services in Scotland''.
But in an article for the Guardian, Lord Birt dismissed that as "make-believe".
Blair Jenkins, a former head of news and current affairs at BBC Scotland who is now chief executive of the Yes Scotland campaign, insisted there was "no credible scenario in which we will not be watching BBC programmes and services we currently enjoy".
But Lord Birt said: "The BBC would no doubt buy some programmes from an independent Scotland. But as with other countries, only programmes in the 'outstanding' category will be purchased.
"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."
The former director general argued that Scottish independence would mean that "fundamental changes to BBC services would be unavoidable".
Lord Birt claimed the BBC "like other national institutions, would lose 10% of its income" after independence.
Combined with recent new obligations on the BBC to fund the World Service and other activities from the licence fee, he added that "in the space of just a few years, if Scotland became independent, the BBC as we know it would effectively lose a quarter of its funding".
Meanwhile, he said the SBS would "have about a 10th of the BBC's current budget" and with a population of some five million to serve would have to "tailor its programmes and services to its modest means".
"A smaller BBC would no doubt make some programmes in and about Scotland, as it does in other countries, but this would be exceptional - unlike now, when as a matter of policy, a proportionate slice of its budget is spent in Scotland on programming for the whole UK.
"So if Scotland were independent, I am sorry to say, it would no longer be much reflected on TV screens and airwaves in the rest of the UK."
He added that while the SBS would wish to "acquire programmes from the BBC, not least those loved by Scottish audiences", maybe commercial broadcasters in an independent Scotland would be prepared to pay more for these, and the BBC would have "no alternative but to act in the interests of its licence payers and to seek the best possible commercial terms for the sale of its programmes".
"As for the availability in Scotland of the BBC's continuing services, there will be some transmission spillover at the border, and BBC channels and services will certainly be accessible more widely in Scotland, but encrypted and available only on commercial terms. One way or another, after independence, Scottish viewers would have to pay to receive BBC services."
Mr Jenkins told BBC Radio Scotland's Good Morning Scotland that a Yes vote would mean the country would have "for the first time what every other normal European country has, which is a national television channel, showing programmes that are relevant to people here".
Mr Jenkins said: "There is no credible scenario in which we will not be watching BBC programmes and services we currently enjoy.
"The bonus is, like other small European countries, we will have our own domestic production base, which means more Scottish content, and definitely more jobs.
"The scare stories we have heard around broadcasting today are among the worst we have heard from the No campaign."
He added that after independence licence fee cash from viewers in Scotland would stay north of the border, which "gives us plenty of scope to have very good national television and radio services".
Mr Jenkins continued: "Domestic broadcasters do a mixture of making their own programmes and buying in programmes and services they want from elsewhere. With the licence fee money, the enormous sums we raise in Scotland, we will have BBC services guaranteed, we will have our own domestic, national broadcaster for the first time, we will have more programmes made for a Scottish audience, more jobs, wider benefits for our creative industries.
"This is a win-win for Scottish people and Scottish production companies."