LABOUR'S humiliating defeat at the Holyrood election was made inevitable by a refusal to overhaul its constitutional position and advocate "home rule for Scotland", the party's deputy leader has said.

Alex Rowley revealed that he had pushed for Scottish Labour to make the case for the devolution of sweeping new powers for the Scottish Parliament and back a move to a federalist model for the UK in its manifesto.

READ MORE: Holyrood 2016: with elections over, what happens next?

However, he found himself overruled by others in the Labour hierarchy, in a move he believes made a devastating defeat, with the party losing a third of its seats and being beaten by the Tories into third place, predictable.

The party, Scotland's dominant political force as recently as a decade ago, began its latest episode of soul-searching as its rivals also came to terms with the new Holyrood landscape following last week's election, which saw voters defy opinion polls and leave the SNP short of a majority.

Nicola Sturgeon faces an early battle with Ruth Davidson's jubilant Tories, now her main opposition, over controversial plans to assign every child a state-appointed 'named person' from August. The SNP leader insisted she had an unequivocal mandate to deliver on her manifesto and refuted claims that an independence referendum over the next parliament is now off the table.

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But as some shifted their focus to next month's EU referendum, questions over the constitution continued to trouble Labour, with Mr Rowley saying his party had been fatally hamstrung by its lack of a clear message on the issue, which he found dominated discussion on doorsteps up and down the country in the election campaign.

He also rejected claims from some Labour figures, such as former MP Thomas Docherty and spin doctor John McTernan (pictured below), that it was a lurch to the left that cost the party support.

The MSP, who lost his Cowdenbeath constituency to the SNP but was re-elected to Holyrood through the regional list system, said that voters on both sides of the constitutional divide felt they were unable to back Labour despite his belief that the party had the strongest policies in other areas.

Mr Rowley said: "We need to define a positive case for the future of Scotland, built around home rule for Scotland. That's where I believe we should be, and where we should have been. But a decision was taken early in the campaign that we weren't going to focus on the constitution because some people believed we needed to put the case for moving on.

READ MORE: Holyrood 2016: with elections over, what happens next?

"I can see the argument for that but it's illogical when the country is in a completely different place. The country hasn't moved on and it looked like we didn't know where we stood. It left us in a position where every time the constitution came up, we looked very uncertain.

"It wasn't going to win back yes voters and no voters felt uncomfortable supporting us too, so it's hardly surprising we're in the position we find ourselves in today."

He did not criticise Kezia Dugdale directly, praising her performance in the campaign and policies on taxation, public services and industry and insisting she had his overwhelming backing to remain in charge, although as leader, she had ultimate responsibility for the position Labour adopted on the constitution.

In a key moment of the campaign, that was ruthlessly exploited by Ms Davidson, Ms Dugdale said she could back Scotland leaving the UK if it was dragged out of the EU before trying to backtrack on her remarks.

READ MORE: Inside the Scottish Labour campaign: no focus, no money, no hope

Mr Rowley's intervention came as Anas Sarwar (pictured below), the ex-MP and a former deputy leader who has been elected to Holyrood, admitted that Labour were "not comfortable nationalists and not comfortable unionists". Mr Sarwar, partially echoing Mr Rowley's comments, said Labour had tried to "move past the independence referendum" when voters were not ready.

Mr Rowley said the party now needed to "reverse the argument" around which powers should be devolved - saying Westminster should only retain control of areas in which it is in Scotland's interest that it did so.

Under his plan, it would see a move to what many would consider a devo-max settlement, although Mr Rowley said he preferred to use the term "home rule", with control of pensions, foreign affairs, defence and some taxes reserved but most other areas to come under Holyrood's remit.

He added: "The constitution in the UK is broken in my view, and we need to build a case for a federal system of government. When you look at strong devolution that is taking place within cities and regions, I think we are moving in that direction.

"Nobody can say it's wrong to have that debate and discussion - I believe politicians are hanging on to something when the country has moved ahead of them. Unless we address the question that's dominant in communities across Scotland then we can't move forward.

READ MORE: Holyrood 2016: with elections over, what happens next?

"In terms of social and economic policies, the Labour Party was in the right place and Kezia was bold enough to do that. She put forward an agenda our candidates were proud of. She is the person to lead the party moving forward and the party is totally united behind her. But we can't ignore the key question that was on everybody's minds at this election - and that's the constitution."