The chief executives of Britain's biggest firms are lasting less than four and a half years in their jobs.

Criticism over fat-cat pay and pressure from investors is threatening those bosses who fail to deliver, according to the financial web site Cantos.

The group said a quarter of FTSE-100 Index companies had appointed a new chief executive in the past 18 months.

Fifty-seven per cent of the top 100 bosses had been in the job for less than three years with only eight per cent in their post for more than a decade.