MP Eric Joyce will not face charges following his arrest over an alleged brawl in a House of Commons bar.
Scotland Yard said it would be taking no further action following the incident earlier this month.
"A man aged in his 50s, arrested on Thursday 14 March on suspicion of assault and ABH in connection with a disturbance in a bar within the House of Commons, and bailed to a central London police station has been released with no further action today," the Yard said in a statement.
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The MP for Falkirk - who now sits as an independent - was detained following a reported fracas during a karaoke night at the Commons Sports and Social Club.
A Crown Prosecution Service spokesman said: “The CPS received a complete file on 26 March in relation to events at the Sports and Social Club within the Palace of Westminster on 14 March 2013, following which Eric Joyce MP was arrested.
“The file related to allegations of assault and after careful consideration we have concluded there is insufficient evidence to charge Mr Joyce with any offences in connection with this incident.
“Although there appears to have been an incident on the evening in question, evidence obtained from witnesses contained multiple inconsistencies and there is insufficient evidence that Mr Joyce committed any offence.
“On this basis, we have concluded there is insufficient evidence to support a realistic prospect of conviction and that no further action should be taken.”
Joyce, 52, was convicted of assault in another parliamentary bar last year and later resigned from the Labour Party.
After admitting four counts of assault he was given a 12-month community order, fined £3,000 and ordered to pay
£1,400 in compensation to his victims.
Following the latest incident, the former Army major was banned by the Commons authorities from purchasing alcohol anywhere in the Palace of Westminster.