A woman who complained she was being paid too many benefits has been told officials cannot send her the right amount - because the computer won't let them.
Her case highlighted the difficulties facing Gordon Brown's flagship tax credits system, which overpaid people by more than £4 billion over two years.
A damning report by MPs condemned "a deplorable situation" which meant struggling families found themselves ordered to pay back money they had been given by mistake.
In the West Midlands, more than 81,000 were pursued by Revenue & Customs after receiving £189 million too much in 2003/04 and 2004/05.
In Birmingham alone, 33,000 residents were paid £38 million more than they should have been.
But the problem has still not been rectified, MP Jeremy Wright (Con Rugby and Kenilworth) told the House of Commons.
He highlighted the case of a Warwickshire woman who had asked officials to stop over-paying her. "Their response is to say, 'We know you're being overpaid repeatedly, but we can't fix the system so that you will stop being overpaid repeatedly.'
He added: "I cannot be the only Member of the House whose postbag is full of complaints from those who have been overpaid, underpaid or in some other way wrongly paid through the tax credit system."
Edward Leigh, chairman of the Commons Public Accounts Committee, said the Government agency responsible for administering tax credits did not understand how the computer system worked. ..SUPL: