Though he was a central part of the New Statesman in its last glory years, he has never shown strong signs of being on the left beyond his support for CND in the 1980s.
When I think of Amis's novels I remember his skewering of the showbiz left in his 1995 novel The Information:
Are you a Labour supporter, the interviewer asks Gwyn.
Of course, thought Richard, yeah of course. Gwyn was Labour. It was obvious. Obvious not from the ripply cornices 20 feet above their heads, not from the brass lamps or the military plumpness of the leather-topped desk. Obvious because Gwyn was what he was, a writer, in England, at the end of the 20th century. There was nothing else for such a person to be. Richard was Labour, equally obviously.
It often seemed to him, moving in the circles he moved in and reading what he read, that everyone in the land was Labour, except the Government.Jonathan Coe has a good article on Amis and Corbyn in today's Guardian.