A leading union has called for an official investigation into a "tax scam" it claimed had led to the loss of £65 million in tax.
Unite said City institutions had delayed making bonus payments to exploit a cut in the top rate of tax from 50p to 45p in April.
The union has called on HM Revenue and Customs to consider whether the law has been broken by the "conscious and deliberate" move to avoid tax.
Steve Turner, Unite's director of executive policy, said: "£65 million in lost revenue while public services face closure and budget cuts is morally wrong.
"Ordinary families will be angered by the millionaires dodging paying their fair share as they struggle with rising cost and falling wages thanks to George Osborne's mishandling of the economy.
"It is a tax scam pure and simple which has defrauded our nation of millions of pounds. HMRC must investigate whether this conscious and deliberate move to avoid tax has broken the law.
"George Osborne has questions to answer too. Did he know that by announcing his tax cut for millionaires early that his friends in the City would seek to avoid paying tens of millions in tax?"