Continuing the roll-out of universal credit has been branded "indefensible" amid reports of further delays to the UK Government's flagship welfare reform.

Scottish Labour said delaying the roll-out is "the absolute least we should see" from Theresa May's government and renewed its call for the process to be halted.

It comes after a BBC report based on leaked documents suggested the roll-out, which has already been beset by delays, could have its timetable pushed back by a further nine months.

The report also claims tentative plans, which could cost hundreds of millions of pounds, are being drawn up to prevent claimants moving onto benefit from suffering hardship.

The SNP pointed out that even if this further delay took place, it would not help people in Glasgow, Edinburgh and Aberdeen - where the new welfare system is being rolled out this year.

Universal credit (UC) merges six separate benefits into one payment, but critics claim flaws in the scheme - in particular the six-week wait for initial payment - are leaving thousands of people destitute.

These issues mean it is not expected to be fully operational nationwide until December 2023 - more than six years later than initially planned.

STV News spent Tuesday speaking to claimants in communities across Scotland, where 29 out of 32 council areas have already begun implementing universal credit.

Derek Kelter, from Glasgow, who is partially sighted, told STV how he had to borrow £1000 from his brother to cover costs while he waited more than six weeks for his first UC payment.

He then had his existing employment support allowance (ESA) cut, costing him £160 a month.

Months later, he was contacted by the government to tell him officials had made an error in calculating his benefit and that he had accrued £1400 in debt he had to pay back.

"It seems to be penalising people with various impairments, that's how it strikes me," Mr Kelter said.

"I'm out of pocket, I don't know how I'm going to exist with this universal credit.

"It's just one obstacle after another."

In Inverness, one of the first areas to pilot the scheme, 40-year-old claimant David Hobbs explained to STV News that covering all his outgoings on the amounts he was getting from UC was "impossible".

He said: "For the first six months I was getting ridiculous payments, like £200 a month, to survive on and that's me paying gas, electric and council tax."

Mr Hobbs had to repeatedly depend on food parcels to get by and said his situation didn't improve until he went to see his MP. "Even then, I'm still struggling," he said.

"I've not spoken to one person who's happy with it," he added.

Speaking in the House of Commons on Monday, work and pensions secretary Esther McVey said the roll-out of UC would be "slow and measured", with more details in the upcoming UK Budget.

The minister conceded last week that universal credit would leave some claimants worse off, after a report by the Resolution Foundation estimated that around 3.2 million households across Britain would be more than £2000 a year out of pocket.

The department for work and pensions (DWP) had been planning to start moving almost four million people, initially in small batches, onto the new system in January 2019.

This will now not happen until later in the year, in a process the government calls "managed migration", with larger-scale migration not likely until the second half of 2020.

Scottish Labour MP Danielle Rowley said: "Universal credit is pushing people into poverty and debt, with seven out of ten sanctions in Scotland falling on young people.

"The roll-out of universal credit has become indefensible.

"Former prime ministers Gordon Brown and John Major warned this would be a Poll Tax moment for the Tories, and even Esther McVey herself admitted people would be worse off under the scheme.

"After months of pressing ahead in the face of the evidence, delaying the roll out is the absolute least we should see from this government."

She added: "The Tories must stop the roll out of universal credit immediately, and deliver urgent answers on how they plan to tackle the many flaws in the system.

"Labour will ensure that our social security system genuinely lifts people out of poverty and is there to support any one of us should we need it."

A DWP spokesman said: "We have long said that we will take a slow and measured approach to managed migration.

"This will not begin in January 2019, but later in the year, after a period of preparation.

"For a further year we will then begin migration working with a maximum of 10,000 people, continuing with our 'test and learn' approach.

"This is to ensure the system is working well for claimants and to make any necessary adaptions as we go."

Commenting on the BBC's report, the spokesman added: "We will publish full plans for the next stage of universal credit roll-out, including managed migration, in due course.

"Anything before that point is speculation and we do not comment on leaks."

The SNP's social justice spokesman Neil Gray MP said: "Universal credit needs dramatic change not just a sticking-plaster solution.

"Only a full halt and radical reform can address the deep-rooted flaws with the system, and help those families who are already suffering in poverty and crisis as a result of this botched Tory policy.

"The UK Government must use the Budget to make immediate changes - including ending and reversing the benefits freeze, reinstating the work allowance, scrapping the two-child cap, reintroducing the ESA WRAC and enhanced disability support, abolishing unfair sanctions, and fixing the payment delays and errors.

"The Tories must also instigate a fundamental review of the entire flawed system, and deliver support for families who have been plunged into debt and rent arrears in areas where universal credit has already been rolled-out."

He added: "Tory plans for a further delay will not help those families in Glasgow, Edinburgh or Aberdeen where Universal Credit is being rolled-out this year - and will do nothing for those people already suffering in the 29 council areas across Scotland where the policy has already been imposed."