Greater London Assembly chairman Trevor Phillips has lined up behind Ken Livingstone’s demand that developments should always set aside 50% for social housing.

Phillips said: “We do have to raise the amount of affordable housing in London. I am not sure that the kind of absolute decree talked about by Ken is the right way to go, but certainly something needs to be done along those lines to solve the problem.”

Former broadcaster Phillips, who earlier in the year threatened to “kick Livingstone’s ass” if he stepped out of line as mayor, told Building that there was a shortage of affordable housing in the capital and strong measures had to be taken to address the issue.

He added: “I think Ken is just a bit unused to dealing with the private sector. He tends to see villains where there are a lot of good guys. That said, developers do need to listen more and learn to work with us. But we must be careful. We as an assembly shouldn’t, and certainly the mayor shouldn’t, jeopardise development in London at this moment in time.”

Livingstone told delegates at a Labour Party conference fringe meeting last week that if housebuilders did not like the idea of setting aside 50% of projects for social housing, they would have to build outside the capital or fund his opponents at the next mayoral election.

Housebuilders have since criticised Livingstone’s plan as unworkable. However, the 50% figure was later confirmed by deputy mayor Nicky Gavron, who is responsible for planning in the capital.