The Trades Union Congress (TUC) has today (15 April) written to the UK Statistics Authority, calling on it to investigate Work and Pensions Secretary Iain Duncan Smith for "misusing" official statistics to justify the government's benefits cap.
Mr Duncan Smith hailed figures published on Friday - which showed that the number to be affected by the £26,000 cap on benefits had fallen by 16,000 - as proof that his welfare reforms were driving people to find work.
However, the government analysis upon which Mr Duncan Smith based his claims explicitly states there is no evidence of people changing their behaviour as result of the cap. It says the main reason behind the fall is because ministers have changed the rules over eligibility.
The TUC says this is not the first time that Mr Duncan Smith has found himself in trouble for misrepresenting statistics.
In January 2012 the UK Statistics Authority rebuked him for his handling of figures on benefits claimed by immigrants. And in 2010 he was criticised by the watchdog's former head, Sir Michael Scholar, for "serious deficiencies" in his use of statistics during a debate on housing reform.
TUC General Secretary Frances O'Grady said: "It was wrong for Iain Duncan Smith to claim that the impending benefits cap has spurred people into finding jobs.
"The government's own analysts say that 16,000 fewer people will be affected because ministers have changed the rules about who is eligible, not because of any change in behaviour.
"The Department for Work and Pensions is a serial offender for misusing statistics. Perhaps ministers should be subject to a three strikes and you're out rule. If you need to make the supporting evidence up, then you must have a pretty weak argument."
She concluded: "It is essential that the UK Statistics Authority investigates Mr Duncan Smith's use of official figures."