The BBC has come under fire for broadcasting "incomprehensible liberal drivel" in a special edition of Radio 4's Today programme guest-edited by the musician PJ Harvey.

The corporation was accused of allowing left-leaning contributors – including the WikiLeaks founder, Julian Assange, and the campaigning journalist John Pilger – to air their views uninterrupted on the flagship radio show on Thursday.

Harvey, who has twice won the Mercury prize, overhauled the show's usual format of Today to introduce song and poetry, including verse by the former archbishop of Canterbury Rowan Williams and Shaker Aamer, the last British resident held by the United States in Guantánamo Bay.

The minister for Wales, David Jones MP, led a stream of criticism online, writing that the programme was "rather unusual". "Have to wonder who extended the invitation," he added. Colin Bloom, executive director of the Conservative Christian Fellowship, lambasted the show as a "train wreck of a programme" and "incomprehensible liberal drivel". And the Daily Mail's columnist Stephen Glover denounced the show as "silly, frivolous and unpatriotic".

Most of the criticism was aimed at the leftwing skew of Today's contributors, including Assange, who used the Thought for the Day slot to defend the leaking of government secrets.

Harvey introduced Assange as a "person of great courage" before the whistleblower cited the recent disclosure of surveillance revelations by the whistleblower Edward Snowden as evidence that governments were aspiring to a "god-like knowledge" about everyone.

Assange, who has been holed up in an embassy in London for more than a year, said in the broadcast: "Knowledge is power. To keep a person ignorant is to place them in a cage. So it follows that the powerful, if they want to keep their power, will try to know as much about us as they can, and they will try to make sure that we know as little about them as is possible."

Kevin Marsh, the former Today editor who introduced the idea of guest editors, described Thursday's programme as "odd". He added: "PJ Harvey is a bit off-the-wall but that's the whole point. It's not as if you're saying this is the Today programme of the future: you're trying to do something that makes people think a little bit ….

"Would I have put John Pilger on? Probably not. I don't know what he's got to say. Assange has got to be interesting even if you don't like the guy. Do you say this man is not allowed on the airwaves? I don't think so."

The Labour MP Diane Abbott welcomed the editorial change, saying Harvey "should do it every day". The Independent's media editor, Ian Burrell, said the programme did skew to the left, but described it as "radical and refreshing".

The BBC said it had received 37 complaints about the programme, but defended its use of guest editors, which it said came "from all walks of life". "The well-established role of the guest editors is to bring their own unique ideas and expertise to the Today programme, working closely with the regular programme team to ensure the material meets the BBC's editorial guidelines," said a BBC spokesman.

This festive season, Today's guest editors have included the Barclays Bank chief, Antony Jenkins; the former MI5 director Eliza Manningham-Buller, the traveller and broadcaster Sir Michael Palin, and Tim Berners-Lee, inventor of the world wide web.