Responding to Treasury figures that says almost one in 10 people earning more than £10 million a year are paying less than the 20% basic rate of income tax, TUC general secretary Brendan Barber said:
"These are truly shocking figures. For too many of Britain's super-rich, tax is something for the little people.
"Unfortunately the Government is making the mistake of trying to deal with tax reform in a piecemeal way - one day rewarding the very wealthy with a cut in their tax rate, the next trying to unpick their allowances that benefit charitable institutions.
"Instead what we need is a proper and comprehensive review of our tax system - one that sets out to make tax fair for everyone and means the super-rich start to pay effective tax rates much higher than the seemingly voluntary rates they pay at the moment."
The government appears to have tied itself in knots over the row on charitable giving.
The row over the cap on a tax relief for charitable giving is the latest in a string of rows that have erupted since the budget.
Charities and philanthropists have warned that Government plans to change the way it taxes charitable donations will discourage giving