In a regulatory statement, the private jet hire and charter broker said: ‘The board of Air Partner has identified, during the course of its year-end review process, an issue predominantly relating to its accounting for receivables and deferred income.

‘Following preliminary investigations, the issue principally relates to the collection of receivables from customers and accounting for uncollected amounts since financial year 2010/11.

‘Certain uncollected receivables were inappropriately offset against deferred income rather than being expensed to the income statement in the appropriate financial year. This is a non-cash item and has no bearing on the company's cash balances.’

The statement said an investigation was ongoing, but Air Partner understands that the cumulative amount between financial year ended 31 July 2011 and the financial year ended 31 January 2018 is approximately £3.3m, and a significant proportion of this relates back to 2011.

The statement concluded: ‘At no point was a customer, operator or supplier impacted or disadvantaged. Further, the group continues to maintain a strong net cash position.’

Air Partner announced in January that it expected annual pre-tax profits to be no less than £6.4m, beating the £5.1m booked the year before.

The group, which employs 250 staff across 20 countries, provides services ranging from luxury private jet charter flights to cargo transport.

According to its 2017 annual report, Air Partner’s external auditor since 2011 has been Deloitte. The firm was paid £208,000 in audit fees last year, plus £26,000 for non-audit services.

Report by Pat Sweet