Details of a new flat-rate state pension thought to be worth £155-a-week will be unveiled later on Monday.

It will replace existing means-tested arrangements for new, but not existing, pensioners from 2015 or 2016.

The current full state pension is £97.65-a-week, but is topped up to ensure a minimum income of £132.60.

This is to be replaced by a new £140 flat rate, with inflation expected to push this up to £155 by the time it comes into effect.

"Tomorrow's pensioners do face a very different world," said Pensions Minister Steve Webb.

"They will, on average, be working for a lot longer, they will be retired for longer, they will not on the whole have final salary guaranteed pensions in the way that perhaps their parents did.

"We therefore need a simpler, clearer foundation because more of them will now be asked to save for their retirement."

Work and Pensions Secretary Iain Duncan-Smith has also indicated that the retirement age will rise to 66 for both men and women by 2020, as European law requires the same age for both genders.