Labour MP Stephen Timms is recovering in hospital after he was stabbed, police said.
A 21-year-old woman was arrested after the incident at Kingsford Way in Beckton, east London.
It is understood the former minister was attacked during a surgery at his East Ham constituency. Mr Timms is a former financial secretary to the Treasury and minister for digital Britain.
A Scotland Yard spokeswoman said: "Police were called at 3.20pm today following reports of a man in his 50s stabbed at Kingsford Way, east London.
"Police and ambulance attended. He has been taken to a local hospital with non-life threatening injuries.
"A 21-year-old woman was arrested at the scene and is currently in custody at an east London police station."
In 2000 Liberal Democrat MP Nigel Jones was wounded and his aide, Andrew Pennington, stabbed to death in a frenzied sword attack during a constituency surgery at the party's office in Cheltenham, Gloucestershire.
Mr Jones, a married father of three, was conducting his weekly surgery when he received lacerations to his hands and arms after fending off blows from Robert Ashman, who was jailed for manslaughter and attempted murder.