Legislation designed to lay the groundwork for future referendums in Scotland, including a possible second independence vote, has been backed in the Scottish Parliament.

MSPs passed the Referendums (Scotland) Bill into law by 68 votes to 54, with two members abstaining.

The legislation, introduced in May, sets out the rules and regulations for referendums north of the border and is intended to pave the way for another ballot on independence.

The new law does not define the issue of when a referendum could be held or what the question would be.

Instead, the Scottish Government also published on Thursday another draft Bill specifically for indyref2, which it will introduce if and when the UK Government grants Holyrood the power to hold another ballot.

Earlier, First Minister Nicola Sturgeon laid out what she called the "clear democratic case" for the transfer of such powers under Section 30 of the Scotland Act, following the SNP's dozen gains in the general election on December 12.

She also wrote to Prime Minister Boris Johnson requesting the transfer of powers from Westminster to her government, although the PM has repeatedly made clear he will refuse the request.

Speaking in Thursday's Holyrood debate, Scottish constitutional relations secretary Michael Russell said: "It's important that rules for any referendums held on devolved matters are specifically suited to Scotland and debated and agreed in this Parliament.

"This Bill therefore addressed a specific gap in the devolved legislative landscape.

"The purpose of the Bill is to put in place a standing framework of conduct and campaign rules."

Russell said the passage of this Bill, along with the Scottish Elections (Franchise and Representation) Bill - which is currently at stage two - will deliver an electoral system in Scotland which is "very much fit for purpose".

However, throughout its passage the legislation has been criticised for not committing to allow the UK’s electoral watchdog, the Electoral Commission, to test any future question in an independence referendum.

The Scottish Government has argued there would be no need to change the question used in 2014, but Russell agreed in November to hold talks with the Electoral Commission on this issue should indyref2 happen.

'The SNP sometimes want to pretend that this is a framework Bill for a referendums in general... we all know that it isn't.'

Adam Tomkins MSP, Scottish Conservatives

But on Thursday, Conservative constitutional relations spokesman Adam Tomkins and Labour constitution spokesman Alex Rowley argued the provisions in the Bill around referendum questions were an attempt to "rig" any future vote.

Tomkins said: "The SNP sometimes want to pretend that this is a framework Bill for a referendums in general... we all know that it isn't.

"It's a paving Bill for a second referendum."

He added: "The only question that Mr Russell is interested in putting to the people of Scotland in a referendum is the independence question."

Tomkins went on to attack the First Minister over her claims the 2014 vote would be "once in a generation".

Rowley insisted Scottish Labour could not support the legislation, adding: "The Bill we are debating today is a Bill to pave the way for an independence referendum to take place next year."

Liberal Democrat MSP Mike Rumbles accused the SNP and Greens of a “nationalist charade”.

He claimed: "The two nationalist parties have fixed the terms of this Bill for their own partisan advantage."

Patrick Harvie, co-leader of the Scottish Greens, said the Bill would "improve the practice, the process, the conduct" of referendums in the future.

He added: "I don't pretend we can solve every aspect of the challenges we're going to face as we approach the next independence referendum, which I believe is coming.

"But I do believe improving the legislation is something we can do today."

After the vote, one politician who abstained, Labour MSP Neil Findlay, said the Scottish Government had a "right" to pursue an independence vote but should wait until the "Brexit implications" are known.

He has been one of a number of high-profile Scottish Labour figures who have recently questioned whether the party should take a hard line against a second referendum following the general election result.

Scottish Labour's health spokeswoman Monica Lennon also abstained, after saying last week that "the future of Scotland must be decided by the Scottish people".