Gordon Brown's tax credits are benefiting the rich, according to figures published by the Conservatives.
The chancellor's flagship policies have taken a battering in recent weeks, with criticism from both the parliamentary ombudsman and Citizens' Advice.
And data from the Tories said that more than 100,000 families with incomes above £50,000 a year are currently receiving the credits.
Of these, some 7,000 have incomes of over £57,500.
The shadow chancellor said Brown "has got a lot of explaining to do why a tax credit system failing so many of the poorest families is also paying out money to thousands of the better off".
"Even before this latest revelation it was clear to all, apart from the chancellor, that we need to take a long hard look at the tax credit system," George Osborne added.
In 2003/04 a total of 112,000 families with incomes over £50,000 were being awarded tax credits - with 72,000 having incomes over £52,500 and 36,000 earning more than £55,000
"We really should be asking ourselves whether taxpayers on average incomes of £15,000 should be providing means-tested benefits to people earning up to £66,000 a year," said Osborne.
"It is time Gordon Brown stopped getting his junior ministers to answer for the failing system and stood up to face the music himself."
