Recently unemployed adults may have to wait five weeks before they get any benefit payments, according to a new report.
The report, published ahead of the latest unemployment figures, said the new five-week wait will apply to anyone making a fresh claim for social security benefits.
The union organisation said it was a "new and deliberate delay" which could distract new claimants from looking for work and drive them into the hands of payday loan firms.
The Government's Universal Credit programme will roll out across more JobCentres from the beginning of next week.
The new payment, which combines six means-tested benefits and tax credits into one benefit, will be expanded across the north-west of England.
The latest figures show that up to March of this year, 6,550 people had claimed Universal Credit.
Almost half of cancer patients are unhappy with the process of obtaining the new Personal Independence Payment benefit.
Macmillan Cancer Support said their survey showed 47% of patients were dissatisfied with the process - a third because of the delays and almost a quarter (23%) because of "poor communication from the Department for Work and Pensions.
Macmillan's head of policy Duleep Allirajah said: "Our report shows the real and shattering impact of these PIP delays are having on cancer patients.
"It is unacceptable that people struggle to heat their homes, are saddled with debt or are left anxious or depressed because they are waiting so long for their much-needed benefits."
Benefits delays are leaving thousands of cancer patients forced to wait months to find out if they will receive help, a charity has found.
A survey from Macmillan Cancer Support found 4,500 cancer patients had been made to wait six months or more for a decision on whether they will get the new Personal Independence Payment (PIP).
The charity said the poll had shown the "shattering" impact of the problems with the introduction of PIP, which has replaced Disability Living Allowance.
The Government has rubbished a report which pointed to benefit cuts as fuel for the rise in food poverty.
It's simply not possible to draw conclusions from these unverified figures drawn from disparate sources.
They cover a wide variety of provision including food redistributed to places such as community cafes, lunch clubs for the elderly and children's breakfast clubs which are frequented by all sorts of people.
This report also overlooks basic facts about the strength of our welfare system. We provide a vital safety net, spending £94bn a year on working age benefits to support millions of people who are on low incomes or unemployed.
The Government must "accept where mistakes in policy and practice are being made" if the surge in food bank use is to be tackled, a major report into food poverty recommended.
The Below The Breadline report said:
The Government must first commit to really understanding and monitoring the true scale of this problem, then set out ambitious steps to tackle it.
This will require a willingness to accept where mistakes in policy and practice are being made, and put in place measures to repair the social safety net.
It will also mean taking steps to ensure that people have decent, secure jobs so that they can earn their way out of poverty and to tackle the rising cost of living.
This will mean visionary policy making; but if these issues are not addressed, many people are going to continue to struggle.
The introduction of Universal Credit and benefit cuts are "a driver of food poverty", according to a report from three major charities.
Oxfam, Church Action on Poverty and the Trussell Trust said, last year over 20 million free meals were given to people at the risk of going hungry because they could not afford food.
Analysis by Oxfam and Church Action on Poverty found that 20,247,042 meals were given to people in food poverty in 2013/14 by the three main food aid providers - the Trussell Trust, Fareshare and Food Cycle - an increase of 54% on the previous year.
The safety net provided by the welfare system seemed to be under threat because cuts to benefits are having a "severe impact on poor and vulnerable families".
The long-term unemployed who have to travel to the job centre every day in order to avoid sanctions on their benefits will be covered for travel by the Government, the Employment Minister said.
Esther McVey told Good Morning Britain the Government would "provide the cost" of travel for those who attend to job centre every day as part of the Help to Work scheme.
"What we are doing here is providing more support for more people. It's costing us money to do this because we believe everybody should benefit and if people can work, they should work."
Two people living off unemployment benefits have spoken to Good Morning Britain about the challenges they face living on benefits.
Casper Gorniok has been unemployed for four years and is forced to rely on his elderly mother for financial support.
He said the tougher measures for the long-term unemployed which start today will give him "less time" to look for a job.
Labour have hit out at the Government for introducing tougher measures for the long-term unemployed but failing to assess the basic literacy and numeracy of benefit claimants.
Shadow employment minister Stephen Timms said:
Under David Cameron's government nearly one in ten people claiming Jobseeker's Allowance lack basic literacy skills and many more are unable to do simple maths or send an email.
Yet this Government allows jobseekers to spend up to three years claiming benefits before they get literacy and numeracy training.
A Labour government will introduce a Basic Skills Test to assess all new claimants for Jobseeker's Allowance within six weeks of claiming benefits.