Barclays has been accused of trying to bury news that it paid its top bankers an "extraordinarily greedy" £39.5m in bonuses by sneaking out the pay details when most of the City was distracted by the budget.

The bank, which promised it was "changing" after being fined £290m last year for its role in the Libor-rigging scandal, gave £17.6m worth of shares to Rich Ricci, the head of its investment banking division. Ricci, who owns 11 horses that raced at the Cheltenham Festival last week including one named Fatcatinthehat, immediately cashed in all of the shares.

The bonus will swell his pay packet so much that means the taxman will collect £9.3m from his next payslip. However, budget day tax changes including the government's decision to scrap the 50p top rate will result in Ricci taking home an extra £27,149 from his basic salary of £700,000 from next month.

Ricci's bonus is worth 656 times the average UK salary, but Wednesday's payday was dwarfed by the £44m in pay and bonuses he collected in 2010.

Barclays chief executive Antony Jenkins, who last month called for a new era of restrained bankers' bonuses, was awarded 1.8m shares worth £5.3m. He cashed in more than half, realising enough money to pay tax on the bonus. A further seven top bankers shared the remaining £16.7m.

The bonuses, which were branded a "staggering reward for failure", come a month after Barclays said Ricci and Jenkins would not be collecting an annual bonus this year because of the Libor scandal.

John Mann, a Labour MP on the Treasury select committee, said the bonuses were "extraordinarily greedy considering the number of people who have suffered because of the banking crisis".

The Robin Hood Tax campaign said: "A scandal-hit bank attempting to bury news of its grotesque rewards on budget day is hardly evidence of a reformed financial sector. This tells you all you need to know – banks cannot be trusted to put their own house in order; the government must intervene to bring them back into line."

Sarah Wilson, chief executive of corporate governance consultancy Manifest, said the bonuses were a "staggering reward for failure". "It's amazing that the bank is paying out such huge sums during its most troubled times," she said.

She accused Barclays of trying to "bury" coverage of the bonuses by announcing them on budget day. "They know everyone is going to be very busy, so releasing the information today is an interesting tactic. There's no two ways of looking at it – they would have known the budget is today."

She told the Guardian the tactic was likely to misfire: "They can't hide it from you, thinking you're going to be too busy writing about the budget to notice it."

A person close to Barclays said the date of the release had been planned long before the budget. George Osborne set the budget date on 11 December. The source said Barclays only realised the clash "within the last few days".

Wilson said corporate governance rules required Barclays to make the release at least 21 days before its annual meeting on 25 April. "They could have released it yesterday, they could've done it tomorrow. They could have done it last week."

"They didn't have to do it today."

John Hunter, a policy member of the UK Shareholders' Association, which aims to protect the rights of private shareholders, said Barclays' decision to release the bonus figures on Wednesday was "sneaky".

"They are trying to bury bad news," he said. "It is a standard PR tactic. It is an attempt to get a story about their massive bonuses off the front pages – you should make a greater effort to make sure the public know about it.

"Society's first reaction is that bankers are a bunch of sleazeballs, and this makes them look even sleazier."