Roll out is reaching the lowest number of claimants since last summer, latest figures show.
The number of benefit claimants registering on the Universal Credit IT system has dropped to the lowest monthly rate since July 2013.
Only 540 people claimed the benefit in May, compared to a peak 1,150 in January, the latest figures from the Department for Work and Pensions (DWP) revealed yesterday.
Universal Credit is meant to simplify the benefits system by replacing six separate benefits with one payment, but it has been plagued with IT problems.
It started being rolled out last spring, and in May and June 120 new claimants each month signed up to the system, then in July 400 people started using it.
It peaked at 1,150 new monthly users in January this year, but figures have steadily dropped since then.
As of May, a total 8,500 people have made a benefit claim on Universal Credit, with 6,570 people continuing to claim.
The rate of the roll out so far led shadow work and pensions minister Rachel Reeves to say the welfare scheme would take until the year 3236 to reach the 5.4 million claimants UK-wide.
She said in a recent speech: "[Work and Pensions Minister] Iain Duncan Smith promised a million people would be on Universal Credit by April 2014. But the latest figures show less than 6,000 people are claiming.
"At the current rate of progress it would take a staggering 1,222 years for Universal Credit to be rolled out across the country."
CBR has contacted her office to check her maths, but has as yet received no reply.
The news comes after Milton Keynes Council admitted staff were struggling to prepare for Universal Credit, due to the lack of clear roll out deadlines.
Anne Jordan, welfare reform programme manager, told CBR: "It's something that's looming away over the horizon. It's difficult to keep the focus. People keep preparing for Universal Credit but it keeps going further away."
Labour is set to pause the project for three months if it comes into power next year. It is broadly in favour of welfare reform but has repeatedly questioned IT issues that saw Duncan Smith restart the scheme in December 2013 after wasting millions of pounds.
The National Audit Office (NAO) found it has wasted £40m so far, with another £91m to be written off by 2018. The watchdog will investigate the project again this autumn.
The Treasury has also not signed off on the project, drip feeding it money instead as it reaches targets.
However, a DWP spokeswoman said the latest figures only reflect the roll out up to May, adding that the total number of claimants is expected to be higher after expanding to 29 more job centres since May.
"Universal Credit is a vital reform that will simplify the myriad of benefits and make work pay and it is on track to rollout safely and securely against the plan set out last year," she added.
"In fact it is already transforming people's lives and is available in a growing number of areas, including 39 Jobcentres, and we are now taking claims from couples too.
"By the end of this year, Universal Credit will be available in one in eight job centres across the country."