The MP for Corby is moving to New York to be with her husband Peter Mensch, the manager of rock group Metallica, and their three children. Her decision will trigger a bi-election in the region.
She wrote to Prime Minister David Cameron saying, "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.
"It is only through your personal intervention, delivered quietly and without fanfare, that I have been able to manage my duties for this long. I am very sorry that despite my best efforts, I have been unable to make the balancing act work for our family."
Mr Cameron accepted the resignation “with regret”, calling her “truly inspiring”.
Mrs Mensch’s profile has been high over the last year or so thanks to her part in the initial inquiries into press standards, following hacking revelations at the now-defunct News Of The World.
She won her seat in 2010 with a majority 1,951, and before that was most famous as a successful author of “chick-lit” novels, under her maiden name Bagshawe.
The bi-election will be held on Novermber 15th.