The Coalition's new flat-rate state pension plan will leave millions of Britons paying "hundreds of pounds more tax" each year, government sources told The Telegraph.
Details of the new scheme, which is set to be implemented in 2017, emerged ahead of an official announcement early next week.
The new system is set to simplify the current one, which sees pensions linked to lifetime national insurance payments. It is set to benefit part-time workers, some self-employed workers, carers and those who take a career break bring up their children.
However, more than six million workers face paying higher National Insurance contributions. The paper said it will affect around 1.4 million workers who are employed in the private sector and enrolled in final salary schemes and contracted out.