A CABINET split has opened up over the choice of SNP candidates for next year's European Parliament elections, the Sunday Herald can reveal.

Four ministers, including Finance Secretary John Swinney, are officially endorsing former Scottish Government special adviser Stephen Gethins for a top job in Brussels.

Deputy First Minister Nicola Sturgeon, who has a history of tension with Swinney, is backing Gethins's direct rival, the party's women's officer, Tasmina Ahmed-Sheikh.

Although he has not made any public statement on the matter, Alex Salmond is also close to Ahmed-Sheikh, a former Conservative candidate and a board member of the pro-independence Yes Scotland campaign, and he is pictured prominently on her website.

The SNP currently have two of the six Scottish MEPs. However, with the Liberal Democrat vote collapsing in the polls, the Nationalists are confident of improving to three next summer at the expense of LibDem George Lyon.

The SNP's 25,000 members are now being asked to rank a shortlist of six hopefuls into the order they will appear on the 2014 ballot paper, which will determine who gets elected.

Ranking opened last week and ends on July 29.

As incumbents, SNP MEPs Ian Hudghton and Alyn Smith are likely to be ranked first and second, all but guaranteeing their re-election.

That leaves the big fight for third place.

It is this scrap which has pitted Gethins head-on against Ahmed-Sheikh, and drawn in Swinney and Sturgeon.

A senior SNP source said Swinney and Sturgeon had a history of spats going back to the end of Swinney's SNP leadership in 2004, when Sturgeon was perceived as briefing against him.

"Those internal tensions were always there, but now they're clearly there for all to see," the source said.

However, another SNP insider said the Euro split was more about the candidates' experience.

"John is supporting Stephen because he worked for him, whereas Nicola is behind Tasmina because she's in Glasgow and she's a women, and the SNP are not very good at gender balance."

Endorsing Ahmed-Sheikh, 42, Sturgeon said that she was "a distinctive voice in Scottish politics, both as a woman with a wealth of experience and as someone who is passionate about Scotland's future in Europe".

Sturgeon added: "She would be an extremely strong voice in Europe for Scotland and the SNP."

Gethins, 37, was a special adviser for four years until January 2013.

Backing him, Swinney said he had "campaigned for the SNP for 20 years and worked tirelessly in the EU and the Scottish Government - He will make an excellent MEP".

Transport Secretary Keith Brown and Energy and Enterprise Minister Fergus Ewing also said Gethins would be an "excellent MEP", while Aileen Campbell, Minister for Children and Young People, said he would be "first class".

A Labour source said: "We know there is no love lost between John Swinney and Nicola Sturgeon so it's no surprise they are battling to build up their own power base for when Alex Salmond steps down after losing the referendum.

"Given Nicola always seem to come out on top of these spats inside the party, Stephen Gethins should be a worried man."

Neither Gethins or Ahmed-Sheikh would comment on the endorsements, but both said they looked forward to campaigning in the election with their fellow candidates next year.

An SNP spokesman added: While Labour are mired in controversy over their candidate selection procedures, the SNP are having a proper one-member, one-vote election to rank our excellent panel of European candidates.

"We are lucky to have such a team of great candidates, and therefore all members of the Government and the wider party will be delighted whatever the result."