Thousands taking jobs 'because of Iain Duncan Smith's benefits cap': He says reforms are changing behaviour Work and Pensions Secretary will publish figures next week showing change Officials found that sizable number of benefits claimants have found jobs Benefits are to be capped at £26,000, the same as national average income Initial assessment found that 67,000 households would be affected by cap But they now believe that figure will be 'dramatically' lower Change: The Work and Pensions Secretary is due to publish figures next week showing that the Government's benefits cap is already 'changing behaviour' even before it is introduced The biggest shake-up of the welfare system in a generation has already encouraged thousands to return to work rather than live a life on benefits, it emerged last night. Work and Pensions Secretary Iain Duncan Smith is due to publish figures next week showing that the Government's benefits cap is already "changing behaviour" even before it is introduced. His officials have found that a sizeable number of claimants have found jobs after being warned that their benefits will be capped at £26,000 a year - equivalent to the national average income. Senior sources say there has been a "dramatic" drop in the number of families due to be affected by the cap, which comes into force on April 15. The Government's original impact assessment concluded that 67,000 households would be affected by the cap in 2013-14, rising to 75,000 in 2014-15. They think this figure is now likely to be "dramatically" lower. A DWP source said: "We have sent out letters to people three times this year if they were going to be affected by the benefits cap. A lot of those people are going back to work. The number who are going to be affected is dramatically lower than we once thought. A lot of people have seen those letters and thought they might as well go out and get a job. Others might have been working in the black economy and decided to go legit. The final figures - still being collated by civil servants - will be a welcome boost to the Coalition, which is facing an onslaught from Labour and special interest groups as more than a dozen changes to the tax and benefits system come into force. What is being billed as the biggest set of changes to state handouts since the formation of the welfare state begins on Monday when council tax benefit will be cut by 10 per cent and people in social housing will see their housing benefit cut if they have a spare room - a policy branded the "bedroom tax" by Labour. The Government's original impact assessment concluded that 67,000 households would be affected by the cap in 2013-14, but his could be 'dramatically' lower On April 6, child benefit will be frozen for the third straight year and real-terms cuts to tax credits will also kick in, with a replacement for disability living allowance introduced on April 8. The shake-up comes amid new claims that the Government's flagship welfare reform - the introduction of universal credit - is in difficulties. The DWP announced on Thursday night that three of the four job centres in the North West of England that had been due to test full versions of the new system from the start of next week will not start their trials in April as expected. Reform: Welfare state begin on Monday when council tax benefit will be cut by 10 per cent and people in social housing will see their housing benefit cut if they have a spare room Only one centre, in Ashton-under-Lyne, near Manchester, would begin to accept claims, with Wigan, Warrington and Oldham following in July. The system is due to be implemented nationally from October. In addition, more than four million small firms have been told they can miss next month's deadline for complying with a new computer system that will underpin the reforms. Universal credit will replace several benefits with a single welfare payment, and is intended to make sure that claimants are always better off in employment than out of work. To ensure that work always pays more, universal credit payments will be adjusted whenever a claimant's income changes, creating the need for a computer system that constantly updates their details. Labour claimed the news about three of the trials was evidence the project was "in crisis." But sources close to Mr Duncan Smith said the Labour claims were "pathetic scaremongering" and stressed that the project is on track. A DWP spokesman said the timetable for rolling out universal credit was "entirely consistent" with a previous claim that it would "go live" in all four areas from April. "Our plan has always been to test universal credit in a safe and controlled way to ensure we get it right for the start of the national rollout in October," he said.