Party’s first Commons member believes politics is changing, leaving colleagues to think on positions ahead of May poll

Rising fears about the electoral support for the Conservatives and Labour at the general election could prompt more MPs to defect to Ukip, Douglas Carswell has suggested.

The former Tory MP, who became the anti-European party’s first MP after winning the Clacton byelection this month, said politicians in both main parties were reflecting on their positions ahead of the May poll.

Carswell said that if Ukip won the Rochester and Strood byelection on 6 November, which has been triggered by the defection of Conservative MP Mark Reckless, the “silent, reflective doubt” would become “something far more kinetic and animated and urgent”.

Carswell told BBC Radio 4’s Week in Westminster: “There’s change coming to politics and I think a lot of them sat there and were thinking about what the future holds for them personally in six months’ time.”

Asked if former colleagues had indicated they were tempted to join Ukip, Carswell said: “It’s clear from conversations I’ve had that some people are thinking about their future … on both sides. I think a lot of people are thinking: ‘Is this a rerun of the SDP or is this perhaps something fundamental and profound.’ I have to keep reminding myself that, actually, it’s neither. So far we have won a single seat, we need to keep a sense of perspective.”

Carswell won almost 60% of the vote in Clacton, but Ukip also came within 617 votes of capturing the formerly safe Labour seat of Heywood and Middleton in Greater Manchester on the same day, a byelection triggered by the death of Jim Dobbin.

Carswell said it felt very different being back in the Commons as a Ukip MP. He has been allocated a windowless office by the Tory whips.

“The real story is how friendly my former colleagues have been,” he said, although there were “one or two people in the whips’ office who are little bit huffy and petty.”

Ukip was hit this week by the resignation of Godfrey Bloom, the colourful former MEP, who warned Carswell to beware of backstabbers among his colleagues.

Bloom said he was leaving Ukip after chairman Steve Crowther banned him from speaking at an event in Wearside. He initially had the Ukip whip withdrawn and subsequently resigned his official role last year, after Nigel Farage said his antics had overshadowed the party’s autumn conference.