The Abbott government's push to double advertising on the SBS during peak viewing periods is part of a plan to sell the public broadcaster, former Liberal prime minister Malcolm Fraser says.

Mr Fraser criticised the government's cuts to the SBS and the ABC, which total more than $300 million over five years.

"Forced cuts from the ABC and SBS … it is part of a whole ideological approach, which to me is to ultimately get rid of publicly funded broadcasting," Mr Fraser said.

"The government does not believe in government activity. They're not prepared to say so straight out in relation to ABC and SBS, because both are too popular."

Mr Fraser's comments after the boss of Ten Network Holdings Hamish McLennan said the government's proposed changes to SBS's advertising structure was creating a "fourth free-to-air network by stealth".

Communications Minister Malcolm Turnbull said government would seek to average out the SBS's current advertising limit of 5 minutes an hour over the day, allowing it to double it in peak viewing periods. This would increase the broadcaster's "savings" back to the federal budget to $53.7 million, or 3.7 per cent, over five years, he said.

"[That is] assuming that the additional revenue to the SBS from advertising changes amounts to $28.5 million over five years," the minister said.

But the commercial free-to-air networks have disputed the government's figures, saying doubling advertising during peak would rob them of more than $200 million.

Mr Fraser said he was concerned that ongoing cuts and more advertising on the SBS would eventually lead to the government privatising the broadcaster.

"They'll say 'what's the point, you're behaving like a commercial [broadcaster], you're getting your money the same way'.

"If there is any value left, they will sell it to somebody or if there is no value left they'll wind it up," he said.

"We are seeing an ideological program designed to get rid of both [the ABC and SBS]."

Mr Fraser said it was "lousy" politics and that the government did "not accept that there were some things that the government needs to do if they are going to be done well".

"I would like to see the ABC operating, certainly throughout Asia, with the kind of reputation that the BBC holds worldwide. And the BBC is one of the most reliable news reporters. It always has been and that's good for Britain.

"The ABC is the only organisation that can do that for Australia."

Mr Turnbull defended the cuts on Wednesday, saying "the work I've undertaken with both broadcasters is about more than repairing the [federal] budget, it is also about reform that will modernise both organisations, pave the way for productivity gains and ensure our national broadcasters are focused on good business practices for the long-term".

Mr Fraser's comments were at odds with commercial network bosses, who say that the ABC should be able to absorb a cut over five years.

John Hartigan, chairman of regional TV broadcaster Prime Media and former News Limited boss, welcomed the Abbott government's push for greater financial transparency and governance at the national broadcaster and also its proposal to strip Mark Scott of the combined role of ABC managing director and editor-in-chief.

"I applaud the fact that editorial responsibility is finally being split or will be split, and even more so, the directors now will have to not sit on the fence," Mr Hartigan said.

"They have got to be active. That's what boards are in place for to represent their constituency, and finally they will have to put up or shut up. You just can't hide. There is no place to hide in today's transparent world."