LEADING Scottish politicians are calling for a UK-wide constitutional convention to draw up a new settlement for the four parts of the British state should Scots reject independence in next year's referendum.

The Herald has been told there is a growing expectation across all three main parties at Westminster that the promise of a comprehensive look at the UK constitutional settlement – should Scots vote No to independence – will be included in the 2015 General Election manifestos of the Conservatives, Labour and Liberal Democrats.

"The independence referendum should not be seen as the end of the process," said Sir Malcolm Bruce, the Liberal Democrat MP for Gordon.

"We have got to a point, assuming after the referendum Scotland stays in the UK, where we have different sets of powers in Scotland, Wales, Northern Ireland and England; in many cases, UK ministers are English ministers. We need a constitutional convention to work out how those powers are best distributed."

Labour's Lord Foulkes, the former Scotland Office Minister, pointed out, constitutionally, there were "a lot of loose ends".

Supporting the convention idea, he said: "All the constitutional changes undertaken by several governments have been piecemeal and we have ended up with a range of anomalies. We now need to look at the constitution in a comprehensive way."

He added: "One of the advantages of having a constitutional convention will be that we can make it clear to the people of Scotland we're going to look at the devolution settlement in a comprehensive way and we will consult the people on what further changes might be appropriate for Scotland."

Eleanor Laing, Conservative MP for Epping Forest, who sits on the Commons Scottish Affairs Committee, also insisted there had been too many "knee-jerk reactions" to constitutional reform. "It's wrong to fiddle about with it for short-term political gain and what we need is a longer-term, broader look at how different issues affect the constitution in different ways."

The Scot said she would "not be surprised at all" if the Tories put such a commitment in their election manifesto.

One senior Scottish Conservative suggested a commitment to a UK-wide convention would be in David Cameron's 2015 manifesto, saying such an inquiry following a No vote made "perfect sense" and was "in line with what the party is saying in Scotland".

The new body – possibly using the 1988 Scottish Constitutional Convention as its model – could draw not only on political parties, but also on the business community, the trade unions, churches, charities and other civic institutions.

In the event of a No vote in the 2014 referendum, it could be established shortly after the next General Election to look at more powers for Holyrood, greater devolution for England, the Barnett Formula and House of Lords reform. Agreement on Lords reform could mean senators for a new-look second chamber being elected in 2020.

Sir Malcolm said he was hoping for a cross-party consensus going into the 2015 election. "I'm looking for a commitment from all parties that they agree this is the right approach, that they recognise a number of issues need addressed and that together we are resolved to look at them."

LibDem colleague Alistair Carmichael, the Coalition's Deputy Chief Whip, said he too was, personally, in favour of a constitutional convention.

"One of the advantages of this approach is that the SNP – which has always refused to work with other parties, whether it was in the previous constitutional convention, on the campaign for a Scottish Assembly or on the Calman Commission – won't have an excuse for sitting it out."

However, an SNP spokesman said: "These calls simply underline that a Yes vote for independence in next year's referendum is the only decision we can take in Scotland which will give Scotland the powers we need to build a strong economy and fair society. A No vote is a vote for nothing; a Westminster veto applies to any further devolution, which we know from bitter experience has held Scotland back."