Hundreds of partners at the UK arm of accountancy firm Deloitte are in line for their biggest payday in a decade despite widespread criticism of Britain’s big accounting firms and their substandard audit work.

The average payout for the 699 equity partners at the firm this year is £882,000. The cash sum covers the year to 31 May and is £50,000 more than they were paid the previous year. Some of the partners will be paid less than the average, but many will be handed more than £1m.

Deloitte has 19,000 staff and 1,070 are partners. However, some 300 of the partners are “salaried” and do not take part in the profit distribution. One in five of the partners are female.

Deloitte is the first of the big four UK accountants to report its 2019 results. The firm’s revenue, which also includes income from Switzerland, increased nearly 11% to almost £4bn and the amount of profit distributed to equity partners was increased from £584m to £617m.

Britain’s big accountancy firms have been criticised by politicians and regulators over lax auditing of companies, anticompetitive practices and conflicts of interest. Scrutiny of the firms increased after a string of corporate collapses including Carillion and BHS – companies which had been given a clean bill of health by their auditors.

Deloitte and its big rivals PricewaterhouseCoopers, KPMG and EY dominate the market for auditing Britain’s largest companies and have used those relationships to sell more profitable consultancy services.

Deloitte last year generated £582m of revenue from audit work, £952m from consulting, and £862m for tax and legal services.

In April this year the Competition and Markets Authority stopped short of calling for the big four to be broken up after a review of “serious competition problems”. Its final report called for them to put greater distance between their audit work and more lucrative consultancy operations to prevent conflicts of interest, but also warned the businesses it would look again at forcing them to break apart if the profession did not improve in the next five years.

In a withering review of the overall audit market, the Financial Reporting Council (FRC) found the quality of Deloitte’s audits declined in 2017-18, although it said the firm had performed better than some others.

Deloitte said it had made investments in its audit practice that would not have been possible without revenues from its other businesses. Deloitte said 84% of its FRC-inspected audits were judged acceptable last year compared with 76% in 2017-18, although that was still below the regulator’s target of 90%.

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Stephen Griggs, Deloitte’s managing partner for audit and assurance, said: “We have been consistent in our support for change in the audit market and are positive about many of the proposals that have been put forward.”

He added: “However, we do not agree with proposals that would see any form of separation of the audit business from the rest of the firm. Audit quality is considerably enhanced by the investment capacity and access to specialists that being part of a much larger and diverse multidisciplinary firm allows.”

Deloitte said its distributable profit increase was caused by one-off gains, including the sale of an investment, and currency swings. Without these items, profit would have been unchanged, it said.