A Stop the War Coalition demonstration against airstrikes in Syria - at which Labour MPs Chris Williamson and Richard Burgon both spoke - featured a performance on stage in Westminster by a guitar duo who performed a song with lyrics that labelled Israel an "apartheid" state and "a living hell".
Derby North MP Mr Williamson was seen applauding as the group completed its performance of a song which referred to "the light of the world, the children which are chosen, the flock have returned, but now with promises that are broken".
The unknown band were introduced to a crowd of around 300 anti-war protesters who gathered in Parliament Square on Monday evening and who clapped as the two male singers sang: "See a land of great divide, see a land of apartheid, see a land of Palestine."
Stop the War organisers had introduced the musical act as a break between a succession of speakers - which also included Labour Kensington and Chelsea MP Emma Dent Coad and CND veteran Bruce Kent - all of whom attacked the decision of the British government to join with America and France to launch airstrikes on Syria.
