Chris Huhne has resigned as an MP after pleading guilty to perverting the course of justice over claims his ex-wife took speeding points for him.
The former Cabinet minister changed his plea on the first day of his trial at Southwark Crown Court over the allegations which date from a decade ago.
The former energy secretary had vowed to fight the charges and last week pleaded not guilty.
However, the 58-year-old admitted in court to doing an act tending or intending to pervert the course of justice between March 12 2003 and May 21 2003.
Mr Huhne announced outside court that he was standing down as MP for Eastleigh. He previously resigned from the Cabinet after being charged last year.
Carina Trimingham, the PR adviser whom Huhne admitted having an affair with in 2010, ending his 26-year marriage, was in the public gallery.
His former wife Vicky Pryce denied a charge of perverting the course of justice.
Liberal Democrat Nick Clegg said that he was "shocked and saddened" by the news, but he felt that Mr Huhne had taken the "right decision" to step down from Parliament.
"This is obviously an extremely serious matter and it's essential that the legal process is now allowed to run its course," Mr Clegg said.