Jack Straw was the UK government's Secretary of State for Foreign and Commonwealth Affairs (usually shortened to "Foreign Secretary") from 2001 till May 5, 2006. He will take over as the Labor Party's leader in the House of Commons.
Unlike similar positions in the US government, this is not a title to be prepended to the last name, as in "Foreign Secretary Straw". Instead, he should be referred to using some form of "the Foreign Secretary, Mr. Straw".
He is a member of the movement within the Labour Party called "New Labour", and was strongly associated with New Labour's involvement with the Bush administration in the push to invade Iraq.