SNP MP Drew Hendry has written to the Prime Minister about the “devastation” being caused by the scheme, which is being piloted in his constituency of Inverness Nairn Badenoch and Strathspey.
A summit is being hosted by Hendry on November 3 and the British leader is being urged to attend to hear some of the consequences of the roll out.
Universal Credit has been slowly introduced across the country and is expected to be fully in place by 2022. Once complete, more than seven million households will receive it.
The brainchild of Iain Duncan Smith, Universal Credit combines six of the main welfare benefits into a single payment, but the scheme has been heavily criticised.
Hendry said in his letter to May that he felt “compelled” to contact her following comments made at Wednesday’s PMQs and said the matter had been “long ignored” by her government.
On Wednesday, Labour leader Jeremy Corbyn called for May to “show some humanity” and make it free to call the Universal Credit helpline.
Calls to the Universal Credit helpline can cost up to 9p a minute from a landline, or between 3p and 55p a minute from a mobile. In Wales the calls are free.
Hendry said that his constituents face difficulties in accessing services online and have to travel long distances, sometimes up to an hour on the bus, to hand in paperwork to the job centre.
He said that “the usual wait on a call is around 30 minutes”.
Inverness was a pilot area for Universal Credit three years ago.
Hendry said that his office has been dealing with more than 200 Universal Credit cases, with more than 60% of his current constituent caseload being Universal Credit-related.
Hendry said that people come to him with “horrifying” experiences.
He detailed the following examples in his letter:
“Abbey had payments stopped when she went on maternity leave. It took our office – having to pass details of law from House of Commons library - to get the DWP to accept their error. Over £2,000 in rent arrears, four months to fix, surviving on food vouchers.”
“Leanne has cancer. This single mum of two - waited 6 long weeks for payment, when it came, it was over £500 short, including £300 for an ESA overpayment that she was never paid in the first place. Shamefully, the DWP then demanded she attended a Work Capability Assessment – against the advice of her furious GP.”
“Rachael was expecting a baby yet she went all through Christmas and on to April without payment. £1,500 of housing arrears and close to being evicted. The DWP said they had a problem with her national insurance number. Against medical advice, your department wanted this pregnant woman, with no money, to travel 200miles from Inverness to Aberdeen and back to sort out your mistakes.”
The SNP MP said he has been urging Westminster for years “to act on the mountain of evidence on the harm this shambles is causing”.
“From pilot to roll out, there has been no attempt to acknowledge or fix the problems that hurt so many,” he added.
In the letter, Hendry tells May: “Many of these people have come to me as a last resort – when they have nowhere left to turn, having already waited months for payment.”
The Scottish MP said there is a “systematic lack of care shown to those most vulnerable in our society”, with burden being placed on the third sector, constituency offices and local authorities.
“I want the Prime Minister to hear from my constituents, local authority staff, and the Third Sector and to work with us to stop this awful mess,” Hendry said.
“On a daily basis now I hear utterly horrifying stories of financial hardships – evictions – and personal humiliation.
“The roll out of Universal Credit has been nothing short of a disaster - and for those it has failed it has been a personal catastrophe.”
Hendry added: “It isn’t working. It never has. The Tories know it and they must halt it now. Theresa May or any of her ministers should really come and hear the testimony from those suffering because of Universal Credit.’’