Many businesses held back payouts, which are normally made in March - when they would have had to pay 50p in the pound to the Treasury - to April so they would only pay the 45p rate.
Bonuses in the finance and insurance industry, which amounted to £0.6bn in April 2012, were at £1.3bn this April.
Chris Leslie, the Shadow Treasury Minister, said: "While ordinary families on low and middle incomes are seeing their living standards fall, those at the top are reaping the benefits of David Cameron's tax cut for millionaires.
"Bonuses soared in April as bankers delayed their payouts to take advantage of the 50p tax cut. Millions of pounds of revenue will have been lost as a result, at a time when people across the UK are facing a cost-of-living crisis."
Frances O'Grady, the TUC general secretary, also blamed Chancellor George Osborne for showering largesse on the better off.
"While ordinary people suffer the longest wage squeeze in over a century, those at the top have seen bonuses rise by a stonking 4%," she said.
"Not content with giving the super-rich a tax cut, the Chancellor has also showered them with an extra gift worth tens of millions of pounds, courtesy of the taxpayer, by giving them plenty of notice to defer their bonuses and avoid the 50p tax rate."
The Office for National Statistics said the usual definition of "bonus season" from December to March did not apply this year with April seeing "unusually high levels of bonus payments".
Total bonuses for the 2012/13 tax year were up 1% to £36.9bn, giving an average of around £1400 per employee, which was unchanged from last year.
Yet there was a much higher rise when taking into account the shift in many bonus payments to the new tax year. Bonuses from May last year to April this year were £38.6bn, up 4%, with the average bonus per employee at £1500 over this period.