However while the disclosure in the New Statesman will undoubtedly upset the Paisley South MP's grieving family, if true it is by no means "irrelevant" to Labour's investigation into Mr McMaster's suicide.
Two factors are said to have driven the 37-year old bachelor to gas himself in the garage of his home at Johnstone, near Paisley, on 28 July - the chronic fatigue syndrome known as ME he had suffered from for 18 months; and a whispering campaign at Westminster and in Scotland that he was gay and suffering from Aids.
Norman Macdonald, editor of the Paisley Daily Express, who served as a councillor alongside Mr McMaster in the 1980s, believes the "big man" - the MP was a rolling 18 stone - could have coped with one or other of the torments, but both was too much.
Mr Brown has widened his investigation to include allegations that two neighbouring Labour MPs, Irene Adams and Norman Godman, were also victims of malicious gossip from the same quarter. Mrs Adams, MP for Paisley North, was falsely accused of having an affair with Mr McMaster and other MPs.
However, the magazine's claim, backed by subtle hints from government sources, that Mr McMaster was indeed gay could allow the lid to be squeezed back on to a bigger political can of worms.
Mr McMaster, Mrs Adams and Mr Godman were allies in a nasty struggle for control of Renfrewshire politics stretching back 10 years. On the other side has been a faction around Tommy Graham, the MP for West Renfrewshire, who was attacked in Mr McMaster's suicide note.
In the extracts of the letter disclosed so far, Mr Graham is not directly linked to the smear tactics and he has denied suggesting McMaster was gay.
Mr McMaster wrote: "I hope Don Dixon [the former Labour deputy chief whip and now a peer] and Tommy Graham can live with themselves ... I would rather be dead with my conscience than alive with theirs." The letter was addressed to his parents and to the Prime Minister and the Chief Whip, but both have refused to publish it.
Labour's Scottish officials stepped in to Paisley three years ago to try and end the civil strife after trade union members and pensioners were being signed up en masse in an area thick with Graham supporters. Jack McConnell, the party's Scottish general secretary, maintained yesterday that Paisley constituencies had been cleaned up even if individual grievances continue to fester.Reuse content