NICOLA Sturgeon is facing calls to release a secret investigation report into a "rotten" SNP branch at the centre of a race row.

The SNP's Coatbridge and Chryston association was temporarily shut down by party HQ this week after North Lanarkshire councillor and Holyrood candidate Julie McAnulty was suspended amid allegations she made racist remarks

But it was also put under investigation in 2012.

Despite members being told at the time that the findings of the disputes committee, which was led by MEP Alyn Smith and also included current MP Tasmina Ahmed-Sheikh, would be reported back to the branch it is understood that, three years on, the conclusions remain buried.

Internal correspondence reveals that Ms Sturgeon, then deputy party leader, was made aware of the row when frustrated members brought the issue to her after pleas to senior office bearers to take action were ignored.

One source said: "It was supposed to be written up and presented but it never appeared. The party knows about the issues but has been completely unwilling to take any action."

Ms McAnulty has significant support within the party from members convinced that the part-time music teacher and church organist would not have used racist language. One described the alleged dirty tricks campaign against her as "project smear".

Scottish Labour said that in light of the recent controversy, the SNP should come clean over the results of the investigation, which concluded in 2013.

A spokesman said: "This branch is becoming a complete and utter embarrassment to the SNP. People in Coatbridge are reading stories of racism, tax avoidance and misuses of public expenses from SNP politicians.

"This whole affair looks rotten and the people of Coatbridge deserve better. The SNP cannot hush a report that may have been critical of Coatbridge SNP councillors and candidates for the Scottish Parliament."

Sheena McCulloch, an SNP activist who works for MSP Richard Lyle, alleged that Ms McAnulty said she wanted to "get the Pakis out of the party" during a car journey last summer. Her complaint was made around nine months after the alleged incident and almost immediately leaked to the press.

Dr Imtiaz Majid, a Muslim North Lanarkshire councillor who tried to become an MP last year but saw his candidacy blocked by SNP HQ, was convenor of the branch when the 2012-13 enquiry took place.

Ms McCulloch said in her complaint to party HQ that she decided to raise the issue after other allegations of racism came to light. It has been claimed that Ms McAnulty refused to sit next to Dr Majid at council meetings and that he complained of racism after she and others staged a walkout of a branch meeting in protest at his election as constituency association convenor. Sources close to Ms McAnulty have said she strongly refutes any suggestion of racism.

A power struggle in North Lanarkshire, one of only four council areas to back independence in the 2014 referendum, has intensified following an influx of new members.

Reports suggest that hundreds of new recruits have deserted the party after being left disillusioned by an SNP cabal that has been dubbed the 'Monklands McMafia', a reference to the 'Monklands Mafia' scandal that hit Labour in the area in the 1990s.

There have been a series of internal disputes around moves to set up new branches which have been resisted by established local power brokers.

An email sent to local party members by MEP Alyn Smith in late 2012, when he announced the probe, stated that he had been asked by the SNP's National Secretary to examine issues in the constituency following "reports about problems that have arisen over the last few months" and asked for written evidence.

He went on to pledge: "The Committee will report back to the National Secretary, and such remedial actions as he and the NEC deem necessary will be carried out."

The SNP has declined to comment.