PRO-independence parties have hit out Scotland in Union's "desperate bid" to prevent them getting elected.

The Unionist group has launched an interactive Better Together-style tool in an effort to stop pro-indy candidates from winning in constituencies in the May 6 election.

In Scotland's electoral system each person is represented by a constituency MSP, elected by the first past the post system. Like seats at Westminster, this means the person with the most votes wins, even if they are not supported by a majority of constituents.

The second half of the system aims to rectify this by balancing each constituency MSP with seven regional MSPs. In practice, this means parties which fail to get a constituency seat can still be elected via the list system.

This is decided by a quick calculation known as the d’Hondt method, which divides the number of regional votes for a party by the number of seats already won in that region, plus one.

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Users on Scotland in Union's interactive tactical voting site are asked to enter their postcode the toll generates which Unionist party they should back in each vote. For instance, in Nicola Sturgeon's constituency of Glasgow Southside it says to vote Scottish Labour leader Anas Sarwar as the constituency vote and Labour, Tories or the LibDems as the list vote.

An SNP spokesperson told The National: "This Labour-Tory alliance just proves that a vote for Labour is a vote to leave the Tories and Boris Johnson in charge of Scotland’s future.

"This is nothing more than a desperate bid from a failing campaign that has no positive policies to offer to improve people’s lives.

"The SNP is the only party with the strong leadership necessary to lead Scotland through this Covid crisis, a clear vision of a recovery, and a positive vision to protect our NHS, create and support jobs, and give every child the best start in life."

Gillian Mackay, Scottish Greens lead candidate for the Central Scotland region, said: "The Scottish Greens will always make the positive case for Scotland's future. That's why at this election we're asking people to vote like our future depends on it; for bold climate action, to deliver a fair and green recovery from the pandemic, and to put Scotland's future in Scotland's hands.

“All the polls show that the Greens can elect a record number of MSPs across the country in May, as part of an increased pro independence majority.

"We'll continue to work hard to win voters' trust, and leave silly attempts to game the election to others.”

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A Scotland in Union spokesperson said: “Polls are clear that a second referendum is not a priority for the people of Scotland and would divide our country.

“But the SNP will use every vote it receives to argue for another referendum on its negative vision to leave the UK.

“If you do not want your ballot paper at this election to be used to divide communities, friends and families, you should consider tactically voting to stop the SNP in your constituency, and voting for one of the three main pro-UK parties.

“Scotland in Union has received requests from supporters for advice on who to vote for to stop an SNP majority."

It comes as the SNP is expected to win 71 seats in the Holyrood election.

A survey by online pollster Find Out Now and political consultancy firm Electoral Calculus for express.co.uk found that voters in Scotland would elect the SNP to lead the Scottish Government in the next parliamentary term.

More than 1000 Scottish adults were asked who they would vote for in their constituency and region if the Scottish Parliament election were to take place now.

Results were then combined and weighted to be demographically representative of the whole country.

READ MORE: SNP set for a clear Holyrood majority as new polling puts Yes ahead in indyref2

Electoral Calculus found that the SNP would gain a comfortable majority of 71 of the 129 seats in Holyrood - higher than the 69 MSPs returned in 2011.

It also found that the independence-supporting Scottish Greens would gain a record 11 MSPs which would mean the Scottish Parliament would have at least 82 pro-independence members in the next parliamentary term.

The Scottish Tories would be the second largest party in the chamber with 24 seats and Labour would come third with 19 total MSPs.

The record performance by the Greens would make them the fourth-largest party and the LibDems would have four members.

Another poll by Find Out Now and Electoral Calculus showed that a majority of those surveyed would vote Yes in a second independence referendum, if it were to take place tomorrow.

It asked voters: “Should Scotland be an independent country?”, the same question posed in 2014.

Results suggested that 48% of Scots would vote Yes while just 44% would vote No in indyref2.

The remaining 8% of voters were either undecided or did not have an opinion.

Removing those who did not have an opinion would return a 52% vote for Yes in an upcoming referendum on Scottish independence.