IFS challenges George Osborne over £12bn welfare spending cut plan

Thinktank says chancellor must specify how he will reach targets announced in the budget, given that the poor had been hardest hit by benefit changes

George Osborne is under pressure from the Institute for Fiscal Studies to specify how he planned to cut welfare spending by 12bn in the next parliament, and warned the poor had lost most from the coalition's benefit changes of the past five years.

Britain's leading experts on tax and spending also said the pickup in living standards hailed by the chancellor in his budget was the slowest in modern history and "no cause for celebration" - although the IFS did suggest living standards on current projections would be higher in 2015 than 2010, a finding that was hailed by Osborne.

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Related: Osborne will need unprecedented cuts in welfare to meet targets, says IFS