Almost 360 roles have disappeared in the past five years, a fall of 20 per cent.

The study suggests that corporate governance guidelines requiring half of a board’s members to be independent are the chief cause of the decline, as companies shed executives to achieve the balance. The squeeze in boardroom opportunities has been exaggerated by a boom in mergers and acquisitions, leaving many executives out of a job.

Caroline Arrowsmith, head of the remuneration team at Deloitte, comments: ‘The changing shape of the board can be a positive thing, leading to more focused and high-quality debate. However, there is also a danger that as the executive element of the board shrinks, the development of strategy is pushed out of the boardroom and into executive committee meetings leaving non-executive directors with a lack of involvement in key decisions.’

The salaries of FTSE 350 directors continue to climb faster than those of the general workforce. The median pay rise for directors is now seven per cent, compared with a rise of 3.7 per cent in the seasonally adjusted average earnings index.

Bonuses are growing even faster. The median payout this year was 94 per cent of salary in FTSE 100 companies, and 75 per cent in FTSE 250 companies, compared to figures of 75 per cent and 60 per cent last year.