JEREMY Corbyn is under pressure to back the scrapping of the UK’s controversial first-past-the-post electoral system as the SNP claimed it gives the Tories “free reign” to make massive cuts to public services north and south of the Border.

SNP MP Tommy Sheppard said the Labour leader should commit to replacing the system, which allowed David Cameron to win an overall majority in the Commons despite polling just under 37 per cent of the vote in last year’s General Election.

Sheppard’s plea to Corbyn will be seen as a fresh attempt by the SNP to work with Labour to oust the Tories, along similar lines to the pledge Nicola Sturgeon made last year that her party was prepared to help “lock David Cameron out of Downing Street”.

The Edinburgh East MP called on Corbyn to sign up to a campaign to “permanently change this broken system”, which means the Tories will remain in power until 2020 despite winning on a minority of the vote in last May’s election.

Sheppard, a member of the SNP’s ruling national executive committee, said it also allowed the Tories to impose austerity in areas such as welfare and defence on Scotland, where Cameron’s party received only 14.9 per cent of the vote and had just one MP elected north of the Border.

The SNP, Plaid Cmyru, the Greens and the Liberal Democrats have all signed the Make Votes Matter declaration – a cross-party campaign to bring proportional representation (PR) to Westminster by 2021.

A referendum on the alternative vote (AV), a preferential system where the voter ranks the candidates in order of preference, was heavily defeated in 2011 when 68 per cent voted to keep the current system.

However, Sheppard said Labour and other anti-Tory parties should back PR, under which a party’s share of the vote is reflected in its representation in parliament.

Sheppard suggested that electoral reform was in the interests of Labour as well as UK democracy, as he called on Corbyn to embrace a shake-up of the electoral system.

He said: “We urgently need electoral reform for Westminster to rectify the democratic deficit. The Tories were voted into government by a minority of the electorate, but now have free reign to cut the income of those with disabilities and destroy lifeline services.

“It is not about individual parties and the advantage they can gain from different electoral systems, it is about having a system that actually reflects the will of the electorate.

“I’d happily give up my seat to give a representative house. It is vital for democratic engagement that people feel they have a stake in the decisions that shape our society, and vital that they feel their vote can contribute to changing them.

“That is why I am very pleased that the SNP has signed up to the Make Votes Matter declaration. We must work with other parties, and excellent organisations such as the Electoral Reform Society, to permanently change this broken system into one which is fit for 21st-century democracy. Now we need the Labour Party to sign up to it too.”

Corbyn has previously said he was open to a form of PR as long as it maintained the link between MPs and their constituencies, stating: “If parties [gaining power] are getting less than 40 per cent of the vote – which seems to be the trend of the last four elections – we have to recognise that.”