Denise Coates, the multibillionaire founder and boss of the gambling firm Bet365, paid herself £323m last year. It is the highest amount ever paid to the chief executive of a British company, smashing the previous record of £265m that Coates set a year earlier.

The 52-year-old’s pay equates to £1.3m for every working day last year. It is 9,500 times the average UK salary and more than 2,000 times that collected by the prime minister, Boris Johnson.

Coates was paid a base salary of £276,585,000 in the year to March 2018, accounts filed at Companies House revealed on Wednesday. On top of this, she collected dividend payments of £45m from her more-than 50% shareholding in the Stoke-based company.

In the last three years alone Coates has collected a total of £817m.

The billionaire was immediately accused of seeking to delay the public release of details of her pay to ensure the publication came after the general election. The Labour leader, Jeremy Corbyn, had promised to “go after” the UK’s wealthy elite and force a crackdown on excessive corporate pay deals.

Luke Hildyard, who campaigns against excessive executive pay at the High Pay Centre, told the Guardian: “This looks like cynical timing, sneaked out straight after a general election campaign where excess wealth, taxes on the rich and the vast gap between those at the top and everybody else have been key issues.

“It’s important that wealth and how it’s created and shared are properly debated. But the publication of these figures seems designed to avoid scrutiny, suggesting that even Bet365 recognises that, while business success should be rewarded, such a colossal payout goes far beyond what is fair or proportionate.”

The accounts had been expected to be filed on or around 20 November and no reason was given for the delay. A spokesman for Coates and Bet365 did not respond to requests for comment.

Bet365 on Monday and Tuesday sent a selected version of its accounts to gambling industry trade publications and warned them not to pass them on to the Guardian or other national newspapers. The websites did not mention her bumper payday.