CONTROVERSIAL benefit reforms have failed to deliver the expected savings in the welfare bill, a leading economic think tank has warned.

The Institute for Fiscal Studies (IFS) said the spending this year will be just £2.5 billion lower in real terms than it was at the start of the parliament in 2010-11 compared to forecast savings of £19 billion.

The findings come as a further headache for Chancellor George Osborne .

He is now preparing to deliver next month's Autumn Statement amid fears that the worsening international economic outlook will add to the strain on Britain's beleaguered public finances.

In its report the IFS pointed to a series of factors behind the failure to achieve the expected reduction in welfare spending.

They include a £5 billion increase in the cost of pensioner benefits - in part the result of the ageing population but also a reflection of the more generous allowances, with pensioners receiving on average £500-a-year more.

Despite cuts to housing benefit, which were expected to produce annual savings of £2 billion, spending is now set to be £1 billion higher - a rise which the IFS said was "unanticipated".