As MPs admitted spending £47 million on advertising means-tested benefits since the 2001 election, opposition parties seized on statistics suggesting people had not claimed £26 billion to which they were entitled.
A report by the House of Commons Library showed that the take-up rate for some handouts had fallen - for example, the proportion of poor pensioners missing out on top-up payments has risen from 25 per cent to 32 per cent.
The Government has repeatedly insisted that it has a duty to run campaigns such as the push by Delaney Lund Knox Warren & Partners on the pensions credit scheme and M&C Saatchi's blitz on the new child tax credit, both of which feature pictures of money. It says that its own research shows the ads have increased both awareness and take-up.
But opposition MPs claim the new statistics show the schemes are too complex and the campaigns are designed mainly to portray the Government in a generous light.
David Willetts, the Tories' shadow pensions secretary, said: "It is extraordinary that Labour has spent £47 million advertising its complicated benefits. That is £15 million a year, five times the adspend when we left office. And there are more pensioners not claiming the benefits to which they are entitled than ever before."