Company executives have seen their pay packets rise by as much as 10%, while workers' salaries have seen only limited increases, according to a new report.
The situation has led to an "unhealthy and growing" gap in wages, the report by the High Pay Centre said.
The findings will likely bolster demands from, among others, Prime Minister Theresa May that companies dial down boardroom excesses.
The study, which looks at the annual reports of FTSE 100 companies, showed the average pay package for a CEO was £5.48 million in 2015, up from £4.96 million in 2014.
Chief executives earn on average 140 times more than their employees, the research shows.
But while executives receive "generous" pay packages, only a quarter of FTSE 100 firms are accredited by the Living Wage Foundation for paying the voluntary living wage to their employees.
The report also shows that of the top 10 highest paid CEOs, none are women.
Stefan Stern, director of the High Pay Centre, said:
Peter Cheese, chief executive of the Chartered Institute of Personnel and Development, said: