A Keighley dinner lady is one of four single mothers who will today take their legal challenge over the Government's controversial Universal Credit welfare scheme to the High Court.

The mums bringing the case claim the payment system for the new benefit is "irrational and discriminatory".

They say the system disproportionately affects single parents, who are mainly female.

Lawyers acting for the women will argue there is a "fundamental problem" with the operation of Universal Credit which is likely to affect "tens of thousands" of people claiming the benefit.

They say claimants are coping with "dramatically fluctuating income" and also suffer financial shortfalls because of a "rigid, inflexible assessment system".

The problem arises when claimants are paid by employers on a date which "clashes" with their assessment period for Universal Credit, according to lawyers.

The challenge, against the Department for Work and Pensions (DWP) is due to be heard on Tuesday and Wednesday by two senior judges sitting in London.

One of the women, 25-year-old Keighley woman Danielle Johnson, works part time as a dinner lady and receives Universal Credit to top up her income.

Speaking ahead of the hearing, Ms Johnson said: "I have never been this financially unstable before, to the point of being unable to afford my rent and having to go into my overdraft when buying food.

"It is getting me into a vicious cycle of debt.

"Universal Credit is supposed to be simpler and fairer, but my experience of it is the opposite.

"I'm doing my best working part-time to make ends meet so that I can look after my daughter.

"I thought the Government was supposed to help and support people like me trying to get back to work but I have found it to be the opposite."

Ms Johnson's lawyers said she is about £500-a-year worse off and struggles to budget in months where she receives no benefit because of the way the system operates.

Another woman, Claire Woods, 30, said she has been forced to turn down a promotion, put her career on hold, use a food bank and incur debt all as a result of the system.

She said: "I invested £40,000 in higher education studies so that I could become an occupational therapist and it's great that I've got my degree but I have had to put my career hopes on hold because of Universal Credit.

"I am competent managing my own finances and am someone who wants to work for professional and personal development, but the assessment period problem meant my income fluctuated so much that it was impossible to budget.

"I wanted to become free of welfare through my chosen profession but Universal Credit is holding me back from that."

Tessa Gregory, partner at law firm Leigh Day - representing Ms Johnson, said: "It is very clear through the multitude of problems reported that Universal Credit is a broken and ill-thought out system.

"It was purportedly designed to assist those in work being paid on a regular monthly basis, yet flaws in the system mean that our client, who has a regular monthly salary paid like many on the last working day of the month, is struggling to support her family.

"She has been left wondering why she ever went back to work, it is an absurd situation.

"Our client has repeatedly asked the government to address this problem, but they have refused to take action, so our client has been forced to take her case to court.

"It is important that this issue gets addressed as soon as possible as once Universal Credit rolls out fully the numbers affected will run into the tens of thousands if not more."

Ms Woods is being represented by the Child Poverty Action Group (CPAG) along with the other two claimants, Erin Barrett and Katie Stewart.

CPAG's solicitor Carla Clarke said: "Universal Credit is promoted as a benefit that incentivises work but in practice its rigid assessment period system undercuts that claim.

"Our clients have been left repeatedly without money for family essentials simply because of the date of their paydays.

"This is a fundamental defect in Universal Credit and an injustice to hard-working parents and their children that must be put right for our clients and everyone else affected."

Universal Credit is a means-tested benefit which replaces other benefits including income support, jobseeker's allowance and housing benefit.

This is the second legal action on Universal Credit to reach the High Court, following a ruling in June that the system unlawfully discriminated against severely disabled people.