They are sometimes referred to as "cafeteria benefits" - a range of salary enhancements from which staff can choose their own preferred package. And companies that have introduced such scemes report higher levels of employee satisfaction.

Up to 400 companies, including all the large accountancy firms and ranging from Cable & Wireless to W H Smith, are now believed to offer flexible benefits. HR specialists are forecasting that the list of choices will grow, even beyond the extensive range now on offer. Typical options include shopping vouchers, cinema tickets, bicycle or bus allowances, health club membership, financial and tax advice, and the more conventional health, dental and travel insurance.

Almost all are rated as benefits in kind, and taxed at the employee’s marginal rate. The main advantage is that they cost less than on the open market, because companies can usually buy in the benefits at a discount. Even so, financial advisers say that employees should check whether they can get similar insurance cover, for instance, more cheaply elsewhere.

Many companies feel that flexible benefits make the total remuneration package more transparent, besides giving employees much more choice - including the option, available with most such schemes, to change their choices once a year.

In the USA, where the system originated, nearly 75 per cent of companies offer "flex benefits". UK companies have been slower to introduce them, chiefly because of the extra administration they involve; but several hundred thousand British workers have now created their own packages in this way, and forecasters say the idea is now spreading rapidly.