Universal Credit is '£600m under budget' and will be offered in all UK job centres by 2016, claims Iain Duncan Smith

Work and pensions secretary claims that DWP is spending £1.8bn on the troubled scheme, rather than the expected £2.4bn

Universal Credit, the scheme designed to merge six different types of benefits into a single monthly payment, is "£600m under budget" and is on course to be offered to all UK job centres by 2016, according to work and pensions secretary Iain Duncan Smith.

The programme has been troubled since its inception, and has been called "completely unworkable, badly designed, and already out of date" by a jobcentre employee, while an IT consultant told Computing that the Department for Work and Pensions (DWP) is hampered by employees worrying about whether the tabloid press will approve of their actions.

But it hasn't just been the technology and IT strategy that have been criticised - the costs of the scheme have been racking up, with at least £130m in taxpayer money being written off from the project.

But Duncan Smith told the BBC that the programme was actually £600m under budget and was implemented gradually on purpose.

"All IT systems in private and public systems, there is always a certain amount of write-down and write-offs. Compared to the expenditure of £2.4bn that was expected, we are now spending £1.8bn, so we are actually spending £600m less than expected," he said.

The government claimed that over 150 more job centres will come on board the scheme in the next two months. It will then be available in all job centres by this time next year, it said.

Duncan Smith said that the national rollout was a "landmark event" that is a key part of the government's long-term economic plan.

The government maintains that once the scheme is fully rolled out it would boost the economy by £7bn every year, because of more people being in work and the subsequent reduction in benefit expenditure.

More than 50,000 people have already claimed Universal Credit, according to the government, and the scheme is currently available in 96 job centres. However, claims from families and lone parents are only being taken in 32 sites.