Theresa May could make a fatal mistake by underestimating Jeremy Corbyn, one of the Conservative premier's MPs warned last night (4 October). Dominic Rabb said his party should be cautious about the left-winger's re-election as Labour leader since Corbyn's victory comes amid a resurgence of anti-establishment politics.

"My overriding feeling is that in this country people are sick and tired of synthetic politics and that maybe explains Corbyn's attraction to the degree that we've seen," he told a Ipsos MORI fringe event at the Tory conference in Birmingham.

The Conservatives are nine points (39% versus 30%) ahead of Labour, according to a September survey from YouGov.

Research from Ipsos MORI in August found May had a net satisfaction rating of +35, while Corbyn scored -33. The pollster said this was a "normal" honeymoon period for a new prime minister.

But Raab pointed out the Labour leader has good honesty ratings because voters consider him as a conviction politician. "Corbyn could be easily underestimated, we underestimate him at our peril," the Esher and Walton MP said.

The comments come ahead of May's keynote speech at the Conservative conference this morning. The prime minister will attempted to claim the centre ground of British politics for the Tories and try to woo traditional Labour voters.

"Time to reject the ideological templates provided by the socialist left and the libertarian right and to embrace a new centre ground in which government steps up – and not back – to act on behalf of the people," May will say.

"Providing security from crime, but from ill health and unemployment too. Supporting free markets, but stepping in to repair them when they aren't working as they should.

"Encouraging business and supporting free trade, but not accepting one set of rules for some and another for everyone else.

"And if we do – if we act to correct unfairness and injustice and put government at the service of ordinary working people – we can build that new united Britain in which everyone plays by the same rules, and in which the powerful and the privileged no longer ignore the interests of the people."