Every song on their third album 'Construction Time Again' is political (with the exceptions of Love, In Itself and More Than A Party). They deal with environmental issues (The Landscape Is Changing), as well as poverty (Shame), nuclear weapons (Two Minute Warning) and revolutions (And Then...) amongst other topics, but it's not exactly deep stuff. You can't blame them, they were all barely out of their teens when they made the album, but they felt they should at least attempt something a little weightier. They had also just returned from a tour of the Far East, and were influenced by a lot of the things they witnessed there.
Other political songs not from CTA would be New Dress (the media), People Are People (prejudice), and probably also John The Revelator (Iraq?). They've held off from politics in recent years though; Martin's seems to be much more comfortable writing about sex, drugs and religion :)