Born in Ayr, Tosh was educated at Kilmarnock Academy and the University of Glasgow, where he was president of the Liberal Club and graduated with a second-class honours degree in history and politics.
In the debating chamber his contributions often tended towards the histrionic: Robert McNeil, writing for The Scotsman, described him as "a great source of unwitting entertainment, gesturing like Mussolini on a balcony, as he wound himself up into ludicrous fits of passion about drains, minor roads and paper-clips.
"[6] In 2001, he announced his intention to stand down at the next election so that he could return to local government, prompting speculation that he was unhappy about the selection of right-winger Iain Duncan Smith as national party leader.
[7] However, he unexpectedly won the race to become a Deputy Presiding Officer that same year, defeating Cathy Peattie by 68 votes to 45, which led him to reverse his earlier decision to leave Holyrood.
[5][8] Press reports attributed his victory to the heavy-handed attempts by the Labour Party leader, Jack McConnell, to force his MSPs to support Peattie en masse, which prompted a backlash from several of them amid public allegations of 'cronyism'.