Malcolm Turnbull has accused the ABC of “too many cases” of inaccurate reporting, claiming that “some” presenters and programs contain a left-wing bias.

Turnbull made the comments to 3AW Radio on Friday, in an escalation of hostilities with the national broadcaster which has been the subject of complaints by government ministers for its reporting of the Coalition’s company tax cut plan and the timing of five byelections.

Asked if the ABC is “captive to the left”, Turnbull said “some presenters, some programs are biased more to the left”.

“But what I’ve found disappointing in recent times is the quality of the journalism, it is the lack of accuracy,” he said.

“The ABC has got an obligation under its act for news and current affairs to be accurate and impartial. Now obviously impartiality is in the eye of the beholder and people have different views, but accuracy is different.

“And I am concerned there have been too many cases of inaccurate reporting.”

Turnbull said the ABC has an obligation to ensure news is “accurate and factual and that if they make a mistake they promptly and prominently correct it”.

On Tuesday the ABC managing director Michelle Guthrie warned that Australians do not want to see the organisation used as a “punching bag” of political, commercial or ideological interests.

The ABC has staunchly defended its record of quality broadcasting and news, launching a new website to make the case for its value to the Australian public after an $84m cut in the 2018 federal budget.

The ABC points to the fact its funding has shrunk from 19.2 cents per person per day in 1987 to 9.7 cents in 2017, during which time it has expanded from one TV station to five, created digital programming from scratch and expanded radio services.

In the month of June the ABC has issued four corrections or clarifications, including one conceding it was “inaccurate” to claim a cashless welfare card holder could not pay back a bank loan because the card would not let her.

A spokesman for the prime minister said Turnbull had “nothing further to add” when asked to substantiate the claim the ABC “often” displayed a bias.

In February the ABC added further information and context to a news story about company tax by journalist Emma Alberici and removed an analysis piece for review after a barrage of complaints from Turnbull, treasurer Scott Morrison and communications minister Mitch Fifield.

But when grilled about its editorial processes at Senate estimates, ABC executives were unable to identify any factual errors in the pieces.

In June Fifield accused three ABC journalists of repeating “false” claims by the Labor party about the degree of government control over the decision of the speaker of the lower house, Tony Smith, to name 28 July as the date for a string of byelections.

On 3AW Turnbull also claimed that the ABC will “never by privatised under any government ever”, continuing a campaign of damage control after the Liberal national council passed a motion to sell all parts of the ABC that did not service rural regions.

“Well I can certainly speak for myself, it’ll never be privatised under any government I lead,” he said.

“In the business of political predictions which is perilous, I think we would agree that the ABC will always be in public ownership.”