Retired police inspector Tom McInally, a former ethnic minority recruitment officer and prospective Labour candidate, said he is "disgusted" by the party's "discriminatory" selection procedures.
All-women shortlists for Labour are often under-subscribed, meaning "a total incompetent idiot would be guaranteed a seat" if she was the only one standing, he said.
Labour said it has "a robust selection process" and "a strong record on promoting ethnic minorities".
Mr McInally reformed Lothian and Borders Police's recruitment policy after the Macpherson Report uncovered police "institutional racism" in 1999. He has previously served in Strathclyde Police and Metropolitan Police.
He has spoken out after two ethnic minority candidates in Edinburgh were apparently sidelined in a seat with only one woman on the "shortlist".
Edinburgh Western and Edinburgh Pentlands constituencies were earmarked as a "one woman, one man" pair, and Labour selected Blair Heary, 27, a parliament aide to leader Johann Lamont, and former care worker and Orcadian solicitor Cat Headley, 29.
Former Edinburgh councillor Shami Khan said he withdrew because he "knew that both seats are fixed by the Labour Party's big leaders".
Mr Khan - who also stood in 2007 and 2010 but was not selected - is Deputy Lieutenant of the City of Edinburgh, a senior representative of The Queen.
He is also chairman of the Edinburgh Mela multi-cultural festival, convener of Edinburgh & Lothians Regional Equality Council (Elrec) and secretary of the Pakistan Society of Edinburgh.
Mr McInally said: "If that's not sufficient to be a candidate for the Scottish Parliament, it's an unbelievable situation.
"I have got no interest in the Labour Party any more because it talks equality but it doesn't serve equality.
"It's discriminatory and I don't think it's the kind of thing I want to be involved with."
Labour has a "friends and family" selection process running "an exclusive list for women without looking at the quality of candidate", according to Mr McInally.
"At that selection meeting the other night there there was only one woman, which means that she was guaranteed to be selected for one of those two seats," he said.
"She (Cat Headley) is competent, but you could have a total incompetent idiot standing and she would be guaranteed a seat.
"There's only 30 or 40 people at these meetings so it can be easily fixed.
"Look around at the selected candidates in Edinburgh and Dunfermline and look at the connections they have, from MSPs' daughters, son-in-laws, very close friends, workers."
Mr McInally said the recent candidate selection fiasco in Falkirk was "down to the lack of numbers in the Labour Party and the ability to nobble the whole thing".
The ejection of disgraced MP Eric Joyce from the party sparked a controversial selection process which became mired in allegations of vote-rigging, igniting a chain of events that ultimately brought the economically vital Grangemouth petrochemical plant to the brink of closure.
Scottish Labour has two MSPs of Asian background in high office, deputy leader Anas Sarwar MP and list MSP Hanzala Malik, who are both from Glasgow.
Mr Khan said Mr Sarwar "is a very good boy, a very intelligent boy, a very good speaker, but he can't do so much in Scotland".
"He would like to bring new people in from minority ethnic communities but he doesn't have any say," he said.
Labour said neither candidate in Edinburgh "have any known relatives in the Labour Party".
A spokesman said: "We have a robust selection process in place which empowers our local members to pick the candidate they believe is best to represent their community.
"Both Blair Heary and Cat Headley are young, talented candidates with strong campaigning records who were chosen by our members in Edinburgh in an open and transparent selection. We have received no complaints about this selection process.
"We are proud of our record on equalities and positive action. We have led the way on gender representation and will do so again in 2016 by twinning our selection so that women have a fair chance to represent us in Holyrood. This has been welcomed by most progressive people.
"We also have a strong record on promoting ethnic minorities and our deputy leader Anas Sarwar is testament to that.
"Currently, we have a number of positive action measures in place for black and ethnic minority candidates.
"We regret that Mr McInally has decided to criticise our selection processes without taking the time to understand them. We wish him all the best.
"If Mr Khan has any evidence of vote-fixing or nepotism, we would be keen that he presented it to us rather than make unfounded allegations."