Conservative MP Louise Mensch is to quit the Commons and move to the United States with her family, she announced today.

The backbencher, who shot to prominence as a member of the Culture, Media and Sport Select Committee which investigated the phone-hacking scandal, said she was "devastated" but that it was a "necessary decision".

The move will give rise to a by-election for her seat in Corby, Northamptonshire, a tight marginal which will prove a major test for David Cameron's Tories.

Mrs Mensch, who was only elected in 2010, has carved out a high profile for herself and had been tipped for advancement at Westminster. But her husband, Peter Mensch, manager of rock band Metallica, lives in New York and she has been forced to divide her time between the UK and US. In her resignation letter to the Prime Minister, mother-of-three 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 Member of Parliament. "It is only through your personal intervention, delivered quietly and without fanfare, that I have been able to manage my duties for this long." Mrs Mensch told Mr Cameron that letting her to work from her constituency on Thursdays and Fridays had allowed her to spend more time with her children. "Unfortunately, it has not proved to be enough. I am very sorry that, despite my best efforts, I have been unable to make the balancing act work for our family," she said. The Prime Minister replied that he was aware it had been "a particularly difficult period for you and your family". "With that in mind, it is with enormous regret that I accept your resignation as the Member of Parliament for Corby and East Northamptonshire, a seat that had been Labour for 13 years before you," he 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 an "inspiring" MP and hinted that she had been in line for a role in the Government. "It goes without saying that I had wished to see you serve for longer and at a more senior level," he said. "But you have made a tremendous contribution in the short period you have served in the House of Commons, and have much to be very proud of." Mrs Mensch, who is one of Westminster's most prolific Twitter-users, took to the microblogging website to say: "I am devastated by the necessary decision that I have had to announce today. It has been an incredible honour serving the people of Corby. "It has, however, proved impossible to balance the needs of my family." Mr Cameron, whose party is at a low ebb in the polls against a resurgent Labour, faces a stiff challenge to retain her Corby seat in the forthcoming by-election. Mrs Mensch - then Louise Bagshawe before her marriage last year - won by only 1951 votes in the 2010 general election. Labour had previously held the constituency since 1997.