Mr Baker, 56, was the only liberal in a right-wing Home Office team, but he insisted his departure was due to an illness, said by friends to be problem with the inner ear.
"It isn't that serious. I have been advised by doctors, if I want to get it right, to take an extended period of rest from ministerial duties," he said.
Mr Baker, MP for Dorset North, will not be resigning his Commons seat. Mr Baker has been an MP since 1979. He was only made junior minister in 1994, after serving as a government whip since 1989. He was responsible for the immigration portfolio. That will be taken over by Tim Kirkhope, a junior whip, who will in turn be replaced by Richard Ottaway, the Parliamentary Private Secretary to Michael Heseltine.Reuse content