14 January 2013 Last updated at 13:08 A new flat-rate state pension likely to start in April 2017 will be outlined by the government on Monday. The weekly payment will be £144, plus inflation rises between now and 2017. But people will have to work longer, making 35 years worth of National Insurance (NI) contributions, rather than the current 30. The pensions minister, Steve Webb, said the new system would be much simpler. "At the moment, nobody has a clue what the state is going to pay them," he told the BBC. We have a basic pension, a second state pension, a pension credit - it's fiendishly complicated. So we are proposing a simple system, not a more expensive one... that will help people plan for their retirements. Now, men and women will build up pensions in their own right. And women coming up to pension age who have got a damaged pension record, because they brought up children, will have that restored," he added. Millions of current pensioners, and those who qualify before the cut-off date, will continue to receive their entitlement under the current system. A universal flat-rate payment in England, Wales and Scotland will be the biggest overhaul of the pension system for decades. It will involve merging the state second pension with the basic state pension, to create one flat-rate payment. It will be paid only to new pensioners reaching state pension age from 6 April 2017 and, for them, do away with the need for the pension credit system. Paul Johnson, director of the Institute For Fiscal Studies (IFS) said: "The self-employed will be the one group who are unequivocally better off in the long run, because at the moment they are not earning any state second pension, and in the long run they will get the whole £144 or so." Chris Curry, from the charity the Pensions Policy Institute, said the people who would benefit from the new system would be those who had traditionally done very badly under the current system, such as women. "[These are] people who don't make enough contributions throughout their working life to, in particular, the state second pension, which includes people with intermittent work patterns, periods of low earnings and the self-employed," he said. Second state pension The benefit of a higher state pension will be partly offset by the requirement to make contributions for longer through NI, in order to get the full amount. Only 474,000 men do so. 3.2 million individuals receive pension credit to supplement their retirement income. The government will also explain exactly how the state second pension, which acts as a top-up to the basic state pension, will be removed. At the moment, some prospective state pensioners will accrue a higher level of state pension than £144 a week, via a combination of their basic and state second pensions. As the government has promised that all their accrued pension rights will be recognised, the new system may have to involve some future pensioners being paid a top-up to the new, merged, flat-rate payment. Final-salary pensions Meanwhile, several million employees in the private and public sectors are opted out of the state second pension because their final-salary schemes pay an equivalent benefit. As a result, they pay reduced NI contributions. The change will bring an end to this system of "contracting out," with two consequences. The government will have to decide if these individuals should receive the full flat-rate pension, if they first qualify for it after April 2017, despite the fact that they will not have not been making full national insurance contributions for the state second pension in the preceding years. The government must also decide if these people should start paying higher NI contributions, after that date, while still in work. Someone on an average wage might have to pay an additional £270 a year but their state pension would also be greater. Paul Johnson said: "At the moment, if you are on a public sector occupational scheme, you are effectively giving up your right to the state second pension." "Under this new system, you would get the full flat-rate pension, plus you would continue to get your public sector occupational scheme," he added. The state pension is expected to continue rising, as now, in line with earnings, prices, or 2.5%, whichever is higher.