Simon Danczuk claimed a "drink problem" led him to send sexually explicit messages to a teenage girl as he faced further lurid revelations about his private life.
The 49-year-old MP added he felt "awful" about lewd texts he sent to Sophena Houlihan when she was 17.
He has been suspended from the Labour Party while an investigation takes place into his conduct, for which he has apologised "unreservedly".
The Rochdale MP also threatened legal action against his first wife, Sonia Rossington, after she made a series of claims about his conduct, calling him a "sexual predator who made my life hell" and revealing details of his drink and drug consumption.
The text messages to Ms Houlihan followed the collapse of his marriage to second wife Karen, who was dubbed the selfie queen after posting numerous photographs of herself in low-cut tops.
The MP for Rochdale told the Sun he felt "lonely" and was "drunk" while on holiday in Spain when he sent the texts.
He said: "I have a drink problem, and that is a major contributory reason why I sent the messages.
"I've seen a psychiatrist about it and he's told me to stop drinking for six months.
"I feel awful about what happened. I don't know what came over me. I'm so embarrassed that I've been such an idiot. I'm sorry for letting my family down and I'm already dreading my young sons finding out when they are older.
The father of five added that "younger women are my Achilles heel" but said he knew sending the messages was "wrong" and his behaviour had "played on his mind".
Miss Houlihan, who is now 18, said Mr Danczuk sent her numerous messages, including one asking if she wanted a "spanking" after she contacted him about a job.
The pair exchanged messages for nearly a month before he asked how old she was, according to the newspaper. He said, at first, he considered it a "professional conversation".
Mr Danczuk's tangled love life has repeatedly made the headlines over the past year, including the ending of a relationship with a Labour councillor, Claire Hamilton, who tweeted after Christmas that she had "dumped" him.
His first wife, Ms Rossington, used a Mail on Sunday interview to claim Mr Danczuk drank a bottle of whisky a night and got "very angry" if there was not a cannabis joint rolled for him when he got home from work.
In a statement Mr Danczuk said Ms Rossington was "obsessed with trying to ruin my political career" and accused her of pursuing a "vendetta" against him.
He said: " These untrue allegations are of a criminal nature and she has chosen not to take them to police but to sell them to a national newspaper.
"The media should be aware that our marriage ended long before our official divorce in 2010. Despite it being nearly 10-years since we've had any kind of relationship, she has not moved on and remains embittered to the point where she has prevented me from seeing or having a close relationship with my children."
He said he had instructed solicitors to act on the contents of the interview.