SCOTTISH Labour's brief period of unity has ended after the former spokesman for Jim Murphy's defeated rival accused the new leader of "abandoning truth" and "making stuff up" about Scottishness.

Stephen Low, who was the spin doctor for leadership candidate Neil Findlay, said Murphy's comments about an "ingrained" Scottish character amounted to him "buying into fantasies".

Murphy beat left-winger Findlay and Sarah Boyack MSP earlier this month to become Johann Lamont's successor as Scottish Labour leader.

Lamont had quit her post in acrimonious circumstances after blasting Westminster "dinosaurs" and accusing UK Labour of treating the Scottish party as a "branch office".

During the contest, Murphy addressed Lamont's claims by stressing his Scottishness and insisting he would take no orders from his MP colleagues.

He said he would hire Yes voters to his team and, 24 hours after winning, promised to rewrite the Scottish Labour constitution to reflect the country's perceived national identity.

Murphy explained: "We are a socialist party yes, but we recognise that our political faith grew out of something deeper which is ingrained in our Scottish character.

"It was there before our party in the ethics of Burns's poetry, the economic vision of New Lanark, the actions of the Highlanders who took on brutal landlords."

However, Low took to Facebook to criticise Murphy's comments, saying of the "ingrained" Scottishness remark: "This is fiction, not history.

"All I can suggest now is that peddling myths - either out of ignorance or calculation, will do us few favours."

He said it was not a "statement that bears any relation to either history - nor the sociology of nations", adding: "We do ourselves no favours by abandoning truth and reality nor buying into fantasies that nations have 'ingrained character'."

Low added: "Are we going to start discussing the ingrained nature of the German or Hungarian or African culture next ... The idea that the labour movement ... arose from a sense of national rather than class identity would get you a bad fail in any history class.

"Jim does, of course, have the right to say what he wants - but when he maintains things that aren't true, the party does have a duty to point these things out."

He accused Murphy of "making stuff up" and concluded with a warning: "We are making a rod for our own backs here."

The leadership contest was broadly good natured but Labour's biggest trade union affiliate, Unite, launched a personal attack against Murphy.

Union general secretary Len McCluskey said Murphy stood for "reheated Blairism", which would be a "sentence of political death for many Scottish Labour MPs" at next year's General Election.

Low was Findlay's press contact during the election and is a policy officer for another trade union, Unison.

SNP MSP Stewart Maxwell said: "The fact that there is a great deal of unease within the Labour party over the election of Jim Murphy will surprise nobody given he is an MP who backs Trident, voted for the Iraq war, campaigned with the Tories in the referendum and has a track record of voting for tuition fees.

"With a recent opinion poll showing that the SNP has actually increased our lead since the election of Jim Murphy, it is clearer than ever that it will take far more than the election of a new leader to address the fact that Labour is fundamentally out of step with people in Scotland."

Low said: "The campaign is over. These views are mine and no-one else's."

A Scottish Labour spokesperson said: "The new leadership team means it's a fresh start for Scottish Labour and Scotland. We will be working together in the new year to take our positive message of radical change all across our great nation."