THE SNP’S frontrunner to claim the hotly-disputed Edinburgh Central seat at next year’s Holyrood election has warned party members “have been let down” after a rule change led to his rival pulling out of the selection contest.

Angus Robertson, who formally launched his bid for the seat last weekend, has called for his party to “unite” ahead of next year’ election - urging his colleges not to be “distracted from delivering independence”.

The call comes after Joanna Cherry officially pulled out of her attempt to be selected for the seat, currently held by former Scottish Tory leader, Ruth Davidson - amid reports the SNP’s ruling National Executive Committee (NEC) could introduce new rules meaning that any MP who wants to stand for Holyrood will have to resign their seat before the Scottish election.

It is further reported that sitting MPs wishing to stand at Holyrood will need to secure at least £10,000 of funding towards the subsequent by-election campaign.

READ MORE: SNP MP Joanna Cherry quits race for Holyrood

Ms Cherry said that would make it “impossible” for there to be a “fair and open contest” to select a candidate for the constituency.

Mr Robertson said the SNP NEC “has made the wrong decision” by changing the rules and has warned against any “interference” in the selection battle.

The strong words come as former MSP and local government minister Marco Biagi officially threw his hat into the ring for the seat which he held from 2011 to 2016.

With Ms Cherry pulling out of the selection battle, it leaves the door open for a two-horse race between Mr Robertson and Mr Biagi.

Ms Davidson is stepping down from Holyrood at May’s election to take up a place in the House of Lords – with the SNP confident of overturning the Conservatives' slim majority of just 610 votes in Edinburgh Central.

But the election battle has so-far been overshadowed by in-fighting between the SNP candidates – leading to Mr Robertson calling for calm.

READ MORE: Angus Robertson launches Holyrood selection bid with dig at SNP rival

He said: "Edinburgh Central SNP members have been let down with some feeling their choices being restricted.

“The SNP NEC has made the wrong decision and must ensure the widest and fairest contest. We need the best candidate to win the nomination without any interference.”

He added: “As former SNP depute leader and business convener of the party, it disappoints me that we are distracted from delivering independence.

“We have to unite and ensure we have the broadest and strongest team standing for the Scottish Parliament. Together we will win.”

Mr Biagi is plotting a return to Holyrood after SNP grass-roots activists asked him to put himself forward after stepping down from the Scottish Parliament four years ago for health reasons.

He said: “Edinburgh Central SNP needs a candidate who can bring members together; one who knows the constituency and its issues inside-out. Above all, we deserve choice.

“Activists have been asking me to stand again for the seat I used to represent. I have now agreed to put my name forward.”

An SNP spokesman said: “The NEC backed an approach that will guarantee constituents a full-time commitment from day one, and minimise the disruption to voters.”