In a setback for Cameron, whose party is trailing the opposition Labour party in most opinion polls ahead of a national election in May, Brooks Newmark said he had written to the prime minister to announce he would be standing down.
"The continued media intrusion into past episodes in my personal life is placing an intolerable burden on my family," the 56-year-old married father of five wrote in the letter.
Newmark, who was born in the United States, announced his decision two weeks after he resigned from a junior ministerial post over a story in a Sunday newspaper saying he had sent sexually explicit pictures of himself to an undercover male reporter posing as a woman.
His announcement that he was quitting parliament came as the Sun on Sunday newspaper said Newmark had sent a second set of nude pictures of himself, to a "young mum".
In the Mail on Sunday newspaper, Newmark wrote that he would stand down at the next election "in response to what seems to be a new text-and-tell story."
"Late at night, I began a series of flirtations in response to approaches from women on social media," he wrote. "Deep inside, I knew I was playing with fire. Now it has consumed me and my family."
He said he was starting residential psychiatric treatment to try to "salvage my life and my family."
The circumstances of Newmark's departure provide more bad publicity for the Conservatives at a time when they are trying to address a growing threat from the anti-EU UK Independence Party.
