Labour can no longer be a party of the status quo on the constitution, one of the party's defeated Scottish MPs has insisted.

Paul Sweeney said the party must look at backing "radical reform" for a more federal United Kingdom.

He spoke out after losing his Glasgow North East seat to the SNP in the General Election.

His comments come after some within Scottish Labour have begun to speak in support of a second Scottish independence referendum.

READ MORE: Analysis: why Labour lost the election

Councillor Alison Evison, who is the president of the local authority group Cosla, said democracy could be strengthened "by enabling the voice of Scotland to be heard through its formal processes", adding that "that must mean a referendum on independence".

Mr Sweeney said while he did not believe independence would be the best outcome for Scots, "we cannot tolerate the status quo any more".

Speaking on the BBC's Sunday Politics Scotland programme, he said the constitutional issues of independence and Brexit had "bedevilled" the Labour Party.

"We're a party that is set up to deal with class and social justice issues, we're not really set up to deliver a particular binary issue on a constitutional question," he said.

"That has really bedevilled us over the last five years because these two big monumental constitutional issues have really split the Labour vote."

The former MP recalled that in the 1980s and 1990s Labour successfully argued that the "dysfunctional" UK necessitated the creation of the Scottish Parliament.

He added that it was still "quite clear the British state as currently constructed is not sustainable".

Mr Sweeney said: "Certainly a more confederal or federal relationship is something that urgently needs to happen and we need to be galvanised to present an argument that that needs to happen, and the British Government needs to recognise that that is a reality.

"I think we need to develop a clear policy that is actually a form of an ultimatum. We say to the British Government: unless you recognise the body politic at large in Scotland is not willing to accept the current status quo of the British state and has to recognise that there needs to be a major engagement with the Scottish body politic to reform the British state and recognise the difference of opinion in Scotland, the United Kingdom is unsustainable.

"I think we need to present that as an ultimatum, you need to present an option on confederation, radical reform, to make the UK a more federal construct."

READ MORE: Never again: growing fears over tactics used in election campaign

Former Scottish Labour leader Kezia Dugdale said the opponents of independence needed to find a new argument for keeping Scotland in the UK.

Ms Dugdale, who stood down as an MSP earlier this year, told No campaigners: "You're wasting precious time arguing about mandates. Last referendum won by persuading centre-left voters 1) EU membership only safe in UK 2) A progressive Labour gov was on the horizon 3) Currency and Economic security.

"Reasons 1 and 2 have melted away and the Yes movement have been working on 3 since 2014.

"You need a new argument for the union which isn't rooted in Queen and country unionism. You need this regardless of whether referendum is next year or in a generation."