London: A 20-year-old student has become Britain's youngest lawmaker in centuries, defeating one of the country's most senior politicians to do it.

Mhairi Black of the Scottish National Party defeated Labour's Douglas Alexander in the seat of Paisley and Renfrewshire South. Alexander, 47, was the opposition Labour's foreign policy spokesman.

She is the country's youngest lawmaker since Christopher Monck, who entered Parliament in 1667 at age 13.

"The people of Scotland are speaking and its time for their voice to be heard at Westminster," Black said after her shocking victory.

She wrote on her twitter account, "Thank you to everyone who turned out and voted for me and helping me win the Paisley and Renfrewshire South #voteSnP."

Black is part of an SNP tide that is sweeping Scotland. The party, which supports independence for Scotland, had only six seats before Thursday's election. It has won 55 out of Scotland's total 60 seats, most of them from Labour.

(With inputs from Associated Press)