Guardian columnist Polly Toynbee will be launching this year’s York Literature Festival on March 19. She spoke to STEPHEN LEWIS.

DON’T try telling Polly Toynbee that average incomes have reached what they were before the financial crash.

Average incomes? she says. You can’t use average incomes as an indicator of whether most of us are getting better off or not – because ‘averaging out’ incomes hides the fact that the rich have got richer and the poor poorer.

“You can put a man with his feet in the fridge and his head in the oven, and say on average, he’s fine,” she says.

Take that, George Osborne.

It is fair to say that Toynbee – the famously opinionated Guardian columnist – isn’t a fan of the Tories. Her new book, co-written with Guardian colleague David Walker, makes that abundantly clear. Cameron’s Coup: How the Tories Took Britain to the Brink doesn’t pull any punches. Toynbee and Walker dive in right from the off, in the introduction.

“Asked why he wanted to be prime minister, David Cameron said, ‘Because I thought I’d be good at it’,” they write.

“He wasn’t. He bears direct and personal responsibility for (nearly) breaking up the UK, because of who he is and the policies he pursued as prime minister.”

What Cameron’s government did on tax and benefits, housing, health and education, they say, “prised further apart region, class, generation, gender and race, driving deeper wedges between town and country, old and young, deserving and undeserving, lucky and unlucky, left and right. And, as it turned out, between the nations that make up the UK”.

Phew. What was that about not liking the Tories?

Toynbee and Walker will be coming to York on March 19 to launch this year’s York Literature Festival. The event has sold out – testament to Toynbee’s drawing power. But the columnist was happy to be interviewed over the phone – after bashing out a piece for the Guardian on Cameron’s refusal to go head-to-head in an election debate with Ed Miliband.

There would be obvious accusations of Cameron seeming a coward, she said – but the Conservative high command won’t worry too much. “They know that will go away.” What gets her goat, she says, is that the Conservatives are constantly describing Miliband as weak and ineffectual. “But if he’s so weak, why won’t you debate with him?”

Not liking the Conservatives is one thing. Calling your book Cameron’s Coup is quite another. Cameron was, after all, legitimately elected, wasn’t he? I ask her.

She comes back quick as a flash: “It was a coup in the sense that nothing he said before the election reflected what he did the moment he got in power.” In the run-up to the election, she says, he tried to portray himself as the compassionate Conservative – the man who would detoxify the nasty party. He wasn’t going to punish the poor or families; or dismantle the NHS.

“And people bought it,” she says. “And it wasn’t true.”

The moment the Conservatives were in coalition with the Lib Dems, they embarked upon a reorganisation of the NHS that was “so big it could be seen from space”.

They also set about dismantling the welfare state, she claims – introducing £12 billion of cuts to benefits that hit the poorest and families with children. On some families, the cumulative impact of all those cuts – including freezes in child tax credits and child benefits, the tightening up of disability benefits and housing benefit – has had a devastating impact. “Nothing that he (Cameron) had said would have prepared you for that onslaught.”

The problem with Cameron, she says, is that he comes from an Eton/Westminster/Home Counties mindset that believes those who are poor must be undeserving.

It is the same myth of the “fat slob lying on the sofa watching daytime TV” that is peddled by right-wing newspapers such as the Daily Mail, she says. For some reason, the fat-cat banker raking in his bonuses while dragging the world to the brink of economic destruction doesn’t have the same resonance.

Organisations such as the York-based Joseph Rowntree Foundation try heroically to counter such misrepresentation of the ‘undeserving poor’, she says. But it only takes one more article in the Mail about a family of 11 on benefits living in a mansion in Kensington to undo all their good work.

Which brings us to Toynbee herself. Her style is famously polemical – opinionated, heated, excitable and anything but unbiased. By pinning her heart so firmly to her sleeve, doesn’t she make it easier for the right wing to simply dismiss her as “just that Polly Toynbee”?

Well, she says, everything she writes is backed up with facts. And she used to be social affairs editor of the BBC in the days of Margaret Thatcher and John Major. “None of them could lay a finger on me for bias then.”

But now, she says, she’s a columnist – so she’s entitled to have opinions and flaunt them: that’s what columnists do. “It’s a different form of journalism.”

And someone in the media has to stand up for the left, she says. “Eighty-five per cent of the national press are owned by three press barons entirely devoted to the interests of the super-rich.” The only ones out there fighting against the tide are The Guardian, The Independent and the Financial Times, she says.

“We’re a thin-sounding voice against all of that.”

Thin, maybe – but impossible to ignore, too.

Watch out for some fireworks when she arrives in York on March 19.

• Cameron’s Coup: How The Tories Took Britain To The Brink. Talk and Q&A by Polly Toynbee and David Walker. Thursday March 19, 7.30pm, at Temple Hall, York St John University. Tickets sold out. The book is published by Faber, priced £9.99.

• The York Literature Festival runs from March 19 to 29 at venues across York. Full details are available at yorkliteraturefestival.co.uk/

Here are a few highlights:

•Saturday March 21, 7pm, St Peter’s School: An Audience with Dame Jenni Murray

•Sunday March 22, 7pm, Grand Opera House: David Starkey: York’s Place In History

•Monday March 23, 7pm, Waterstones: York author Matt Haig (author of The Humans) on ‘reasons to stay alive’

•Monday March 23, 7.30pm, Quaker Meeting House: An Evening With The Minster Men. A celebration of York City Football Club, with former City legend Chris Jones, York Press sports reporter Dave Flett and Radio York’s Sharon Shortle

•Saturday March 28, 10.30am, Quaker Meeting House, Friargate: York Writers presentation: Breakfast with Tracy Rees.Tracy was once an active member of York Writers. She has now returned to her native Swansea, but remains a member of the group. She was the winner of the inaugural Richard & Judy Book Club ‘Search for a Bestseller’ competition’ and her book Amy Snow – set in early Victorian England – is due for publication later this year.