A 20-year-old student representing the pro-independence Scottish National Party (SNP) was elected Britain's youngest lawmaker since 1667 Friday, toppling one of the opposition Labour party's top figures.

Mhairi Black defeated Labour's election campaign chief Douglas Alexander in Paisley and Renfrewshire South as an exit poll indicated that the SNP could win 58 out of 59 seats in Scotland.

At the age of just 20, Black has become Britain's youngest member of parliament since 1667 in a victory which symbolises an expected nationalist landslide in Scotland.

Black still has to complete her final exams at Glasgow University but will now be putting her politics degree into practice as the pro-independence Scottish National Party (SNP) MP for Paisley and Renfrewshire South.

The no-nonsense blonde, who pronounces her first name "Mary", won a majority of over 5,000 in Thursday's election to topple Douglas Alexander, the Labour party's 47-year-old foreign affairs spokesman and campaign chief.

As the result was announced, a roar of approval went up from her supporters at the count centre but Black spoke in a steady voice as she vowed to improve life for ordinary Scots.

"We will work to put an end to the austerity cuts that are hurting people in communities both north and south of the border," she said.