Less than two weeks after Britain’s biggest blackout in a decade, National Grid has confirmed that it has given its chief executive a £1m pay rise over the last financial year to reward his “strong performance”.

The company’s annual report, which was republished on Monday, shows that John Pettigrew was paid £4.56m for the financial year to the end of March, up from £3.65m the year before, for delivering value to shareholders.

The payday windfall came as National Grid prepares to publish an interim report on the 9 August blackout, which left almost a million homes without electricity, and hundreds of thousands of people stranded in rush-hour travel disruption. The report is due to be released at 7am on Tuesday.

National Grid faces serious questions from the regulator and the government but has topped up Pettigrew’s £944,000 salary with a bonus of the same size.

Pettigrew, 50, has also received a long-term bonus of almost £2.25m, which is almost £1m more than the £1.5m he was given last year. He also received £283,000 towards a pension and benefits in kind valued at £94,000.

National Grid’s remuneration committee said Pettigrew has “continued to deliver strong performance in his third year in the role” and delivered value to investors and shareholders.

• This article was amended on 20 August 2019 to clarify that National Grid first revealed its chief executive’s bumper pay to investors and shareholders in June, before their AGM in July. The company’s finance division republished the report on Monday.