Watson was elected to the Parliament of the United Kingdom as Member of Parliament (MP) for Glasgow Central at a by-election in 1989, following the death of Bob McTaggart MP. He was re-elected in the 1992 election and represented that constituency until it was abolished in 1997. He sought the nomination from the Labour party to run for the Govan seat at the 1997 election, but after initially winning the nomination by one vote, he lost a re-run to Mohammad Sarwar.