Ken Livingstone has said Labour MPs who voted in favour of airstrikes in Syria should be prepared to be deselected as candidates for the next election.
The former London mayor said: "When I was the MP in Brent East the right wingers wanted to get rid of me, they ran candidates against me. I didn't say it was wrong for them to do that.
"They had the right to have an MP that reflected their views. I managed to win, but it gave the party membership a vote on it and i think that's absolutely right."
The shadow chancellor warned it could foster another generation of militants determined to commit a Paris-style terror attack.
The Defence Secretary has warned the RAF that the fight against Islamic State will not be short or simple.
Officers were posted outside the constituency office of Neil Coyle, the Labour MP for Bermondsey & Old Southwark.