Iain Duncan Smith's Department for Work and Pensions has been rebuked by the statistics watchdog over a claim that more than 12,000 households have found work or stopped welfare claims because of the benefit cap.
The UK Statistics Authority found that while the figures for claimants moving into work and stopping claiming housing benefit were accurate, the DWP did not have evidence that the individuals took the decision because of the £500-a-week cap on most welfare payments.
The Authority's chairman Sir Andrew Dilnot urged the Department to "exercise caution" in future claims about the impact of its policies.
UKSA director general for regulation Ed Humpherson, who analysed the statistics behind the DWP announcement last month, found that "the available numerical evidence does not demonstrate a particularly strong causal link between the benefit cap and the decisions made by individuals about moving into work".
While the figures were "consistent with some people moving into work because of the benefit cap", they do not demonstrate "clear causality", he said.
The Statistics Authority also criticised a Treasury document setting out the increase in female employment in different sectors of the economy.
A bar chart produced by the Treasury showed a 23% increase between 2010 and 2014 in women working in agriculture and mining and a 14% increase in manufacturing, both towering over a much smaller bar showing a 5% rise in female workers in the service sector.
However, the 571,000 increase in jobs in the service sector - which employs many more women - was far larger than the 38,000 rise in agriculture and mining and 91,000 in manufacturing.
In response to a complaint from the TUC, Mr Humpherson found that the chart was not "fully satisfactory" and "although numerically correct, might mislead the non-expert reader". Government announcements based on official statistics should be accompanied by an explanation of how the sources have been used, he said.