Louise Mensch to quit as an MP, triggering Corby by-election

Conservative politician and novelist Louise Mensch is to stand down as an MP, the party has announced.

The MP for Corby is moving to New York with her three children to be with her husband of a year, Peter Mensch, who is manager of rock band Metallica.

Her decision to quit will trigger a by-election in the Northamptonshire constituency, a marginal seat.

Before entering politics she made her name as a best-selling chick-lit author, under her maiden name Bagshawe.

The MP, who won her Corby and East Northamptonshire seat in 2010 with a 1,951 majority, said she was finding it increasingly difficult to juggle family responsibilities with her political career and her decision to quit politics was "devastating but necessary".

The by-election is expected to be held on 15 November - the same day as elections for police and crime commissioners are held across England and Wales.

It is the first Conservative-held seat to be contested since the 2010 election and will be a major test for David Cameron and the coalition.

The BBC's Political Correspondent Carole Walker said the election was likely to be "awkward" for the prime minister - coming at a time of economic and political difficulties for the government.

Writing to the prime minister to announce her resignation, Mrs Mensch said: "As you know, I have been struggling for some time to find the best outcome for my family life, and have decided, in order to keep us together, to move to New York. With the greatest regret, I am thus resigning as a MP."

She thanked the prime minister for his support during her time in Parliament, saying it had been an "honour" to fill the role.

"It is only through your personal intervention, delivered quietly and without fanfare, that I have been able to manage my duties for this long."

But she added: "I am very sorry that despite my best efforts, I have been unable to make the balancing act work for our family."

In his response, the prime minister said it had not been an "easy decision" for the MP.

"It is with enormous regret that I accept your resignation as the MP for Corby and East Northamptonshire, a seat that had been Labour for thirteen years before you," the PM said.

"I do so only because I wish to support you in acting in the best interests of your family, which must come first."

Mr Cameron said Mrs Mensch had been a "truly inspiring" MP and had helped "bring politics alive to those outside the Westminster Village" thanks to her "effective appearances on the television and use of social media".

Mrs Mensch told the Northamptonshire Telegraph that "when I first took the post I was in a different position but sometimes life throws you a curve ball that you didn't expect".

She is one of the highest profile Conservatives from the 2010 intake and has been in the spotlight as a member of the Commons culture committee which has been investigating phone hacking and questioned Rupert and James Murdoch among others.

Her profile has been further boosted by a series of outspoken comments on Twitter, which have led to rows with Piers Morgan and other public figures.

Mrs Mensch was a prolific user of the micro-blogging site with 102,000 followers.

But she said recently she had grown "frustrated" with it and has set up a rival site - Menshn - which aims to keep conversations on topic and allow people to post 180 character messages - 40 more than Twitter.

Earlier this year, a 60-year-old Gloucester man was convicted of sending a death threat to the MP by e-mail, threatening her children. She said she had been "very upset" by the incident.

Several MPs took to Twitter to praise Mrs Mensch for her contribution to Parliament and for drawing attention to the problems MPs faced in meeting their professional and personal responsibilities.

Fellow Conservative Amber Rudd said Mrs Mensch had been a "well-liked, extremely capable and punchy" presence in the House of Commons.

But she told Radio 4's The World at One the MP could not carry on "representing her constituents from America" and her situation was not necessarily similar to other MPs juggling work and family.

And Brian Binley, who represents the nearby constituency of Northampton South, said aspiring MPs needed to understand the "stresses and strains" that came with the job and warned against a "cult of youth" when it came to choosing parliamentary candidates.