High-profile Conservative MP Louise Mensch is to leave parliament to move to New York with her family, she announced Monday.
Mensch, 41, a prominent presence on Twitter who recently set up her own social network, tweeted: "I am devastated by the necessary decision that I have had to announce today... It has, however, proved impossible to balance the needs of my family."
Since her election in 2010 Mensch has become a well-known Conservative figure and was seen as a potential minister.
Her husband Peter Mensch, the manager of hard rock band Metallica, lives in New York.
They were married a year ago in Manhattan, but Louise Mensch has three children from a previous marriage who live with her in Britain.
In June she set up her own social network, a Twitter-like network called Menshn with a politics focus that is divided into threads by topic, along with former Tony Blair aide Luke Bozier. On Twitter itself she has more than 100,000 followers.
She has also published 14 "chick-lit" novels under her maiden name, Louise Bagshawe.
In her resignation letter to David Cameron, 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."
She added that being allowed to work from her constituency two days a week had enabled her to spend more time with her children, but "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."
Cameron said he was accepting her resignation "with enormous regret".
"It goes without saying that I had wished to see you serve for longer and at a more senior level," he responded.
"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."
Her departure will trigger a by-election in the marginal Corby and East Northamptonshire seat, which was Labour-held for more than a decade before Mensch's election.
It is likely to be a tough battle for the Tories, who, with the country in recession, are around ten points ahead in most opinion polls.
Mensch has also made headlines by admitting she had taken Class A drugs in the past, telling a BBC Question Time debate that they had "messed with her head" and left her with "long-term mental health effects".