Falkirk MP Eric Joyce has been arrested after "clashing" with a teenager in a London shop.
The Metropolitan Police service said a 54-year-old man had been arrested on suspicion of actual bodily harm following the incident at a convenience store in Camden.
Mr Joyce released a statement confirming that he had spoken to police at the store on Friday 17 October.
The matter has been referred to the Crown Prosecution Service.
A Met Police spokesman said a 14-year-old boy was also arrested at the scene for possession of cannabis, and was taken to a central London police station for questioning along with the 54-year-old.
In a statement posted on his website, Mr Joyce claimed he had asked for police to be called after he had "detained a youth".
He said officers who questioned him said the CPS and Met Police press office would be informed "because of my identity".
He added: "I will make no further comment for now, other than to say that no alcohol was involved, and I am not in the habit of summoning the police if I feel that I am in the wrong."