THE Scottish Conservatives are facing a long and "nasty" bout of in-fighting, with leader Ruth Davidson backing an inexperienced friend against a party veteran to be Scotland's next Tory MEP.

Senior party sources say the expected retirement of Scotland's sole Tory MEP, Struan Stevenson, has created a frenzy of interest in standing for Brussels.

Applications to stand for the Tories at the next European elections in 2014 close tomorrow.

Davidson is understood to favour Dr Ian Duncan, the clerk to Holyrood's European Committee, while Stevenson believes his assistant, Belinda Don, would make an extremely able candidate.

In addition, Davidson's deputy leader, MSP Jackson Carlaw, is backing a third candidate – his policy adviser, Stuart McIntyre – setting the scene for a messy three-way squabble.

"It's shaping up to be a Class A disaster for the Scottish Conservatives," said one party member.

One of six Scottish MEPs, Stevenson, 64, can wait until next year before announcing whether he will run again. However, there is a near universal expectation he will retire.

His exit would open up a vacancy at the top of the Tory candidate list for Europe, a position that virtually guarantees election. Stevenson's salary, expenses and pensions package in 2010 came to just less than £200,000.

"People will be popping out of the woodwork for this because they'll see it as a bit of a cushy number," said one senior Tory.

"You could look at the list of failed parliamentary candidates – which is a very long list – and pick every name off it."

Don, 54, should in theory be favourite to replace her boss. However, she opposed Davidson being party leader last year, instead supporting rival candidate Murdo Fraser.

Duncan, the clerk to Holyrood's European and External Relations Committee, stood for the Tories in Aberdeen South in the 2003 Holyrood election but has since kept away from frontline politics. Meanwhile, Carlaw is backing McIntyre, his former election agent in East Renfrewshire.

"It's going to be nasty," said one senior Tory. "Belinda thinks she's got it in the bag, but she's toast."

Final selection is expected in spring 2013.