The Scottish parliament was expected to vote for a second independence referendum on Wednesday -- amid dire warnings about the damage that ongoing constitutional wrangling was having on Scotland's economy.

Lawmakers were set to back First Minister Nicola Sturgeon's call for a second referendum when they vote following a two-day debate in the semi-autonomous assembly in Edinburgh.

British Prime Minister Theresa May has suggested she will rebuff Sturgeon's demand for a referendum re-match before Britain leaves the European Union.

May insists "now is not the time" while she spends the next two years striving to secure a good deal on Brexit, once the EU Lisbon Treaty's Article 50 departure process is triggered on March 29.

But Sturgeon said on Tuesday it would "wrong, unfair and utterly unsustainable" for May to stand in the Scottish Parliament's way.

On Wednesday, Strathclyde University's Fraser of Allander Institute warned both sides that their ongoing squabbles were hammering Scotland's economy.

"The Scottish economy has now been stuck in a low-growth cycle for nearly two years," the think-tank said.

"With the triggering of Article 50, and plans for a further independence referendum, the Scottish economy's resilience is likely to be further tested over the next year."

Institute director Graeme Roy called on both the Scottish and UK governments to "provide clarity and reassurance" over independence and Brexit respectively.

He said: "The increase in uncertainty caused by the triggering of Article 50 and the prospects of a second independence referendum will act as a headwind for many businesses."

Former Bank of England governor Mervyn King warned independence "would be expensive" for Scotland.

King, who headed Britain's central bank between 2003 and 2013, told the BBC that Scotland "certainly" could be independent, but "it would be a challenge to borrow on the international market if Scotland decided to run a large budget deficit".

As leader of the governing, pro-secession Scottish National Party (SNP), Sturgeon has been a champion of independence although she needs the green light from London for a legally-binding referendum.

Winning the Scottish parliament's approval would pave the way for her to ask the British government for the powers to call another vote.

Scotland rejected independence in 2014, although the SNP argues Britain's decision last June to leave the EU warrants a fresh referendum as a majority in Scotland voted for Britain to remain within the bloc.

May accused the SNP of "divisive and obsessive nationalism" on Friday.

The premier has said she aims to get the best divorce package from Brussels for Scotland and the wider United Kingdom, with formal Brexit proceedings to be started by the government on March 29.

Sturgeon has suggested a second referendum should be held by early 2019 at the latest.

This would see a vote take place before Britain leaves the EU, although the first minister has left room for negotiation on an alternative timetable "within reason".

The SNP runs a minority government in the Scottish Parliament.

However, it has the support of the pro-independence Scottish Greens in Wednesday's vote, bringing it the majority needed to outnumber the unionist Scottish Conservative, Labour and Liberal Democrat parties.

The Greens' manifesto says there should only be another referendum if it comes about "by the will of the people" and not "calculations of party political advantage".

Despite Sturgeon's ardent drive for a second referendum, current polls show she may not win such a vote.

The September 2014 referendum saw Scotland reject independence by 55 percent. A ScotCen social attitudes study published last week found 46 percent now support independence.