The pay of FTSE 100 bosses surged 11 percent in the past year, pushing their median pay up to nearly £4 million ($5.1 million), according to a report which also found full-time employees received a 2 percent rise over the same period.
The report comes at a time of growing shareholder activism over big pay-outs, with companies including BT, Royal Mail and WPP all being forced to contend with stormy annual investor meetings over recent months.
The research, published Wednesday, by the Chartered Institute of Personnel and Development (CIPD) and the High Pay Centre showed a full-time worker on a median salary of £23,474 would need to work 167 years to earn the median annual pay of a FTSE 100 chief executive — up from 153 years in 2016.
"When CEOs are happily banking ever larger bonuses while average worker pay is squeezed, then something is going very wrong," said Rachel Reeves, a lawmaker from the opposition Labour party who chairs the business, energy and industrial strategy committee, which is leading an inquiry on fair pay.
"Recent revolts on pay awards show that shareholders are increasingly sharing this frustration at unjustifiable pay awards … If businesses don't step up on executive pay, then (the) government will need to step in," she added.
'Deeply unsettling'
In an effort to combat unequal corporate pay-outs, Britain's government announced that from 2020 large listed companies in the U.K. would be required to publish and justify the pay gap between chief executives and staff.
The measure is also designed to put pressure on businesses to explain precisely how share price movements could impact future executive pay.
Nonetheless, despite government efforts to reduce runaway salaries for bosses of the U.K.'s largest companies, the pay gap between bosses and workers has widened over the past 12 months. The highest paid CEO in 2017 was Jeff Fairburn at the housebuilder Persimmon, who received more than £47 million in 2016 — around 22 times his 2016 pay.
The report showed Simon Peckham of engineering turnaround specialist Melrose Industries ranked second on the highest-paid list, banking £42.8 million in 2017 — equal to 43 times his 2016 pay.
Persimmon and Melrose Industries were not immediately available for comment when contacted by CNBC on Wednesday morning.
Meanwhile, women were found to represent just 7 percent of FTSE 100 bosses and accounted for just 3.5 percent of their total pay. In fact, the report said a FTSE 100 chief executive was just as likely to be named a variation of David or Stephen as they were to be a female CEO.
"It is deeply unsettling that such a substantial pay gap remains between CEOs and ordinary workers," Luke Hildyard, director of the High Pay Centre, said in a statement.
"Big CEO pay increases reflect poorly on corporate culture and accountability and suggest that bolder reforms to corporate governance may be needed. In this light, the weakening of plans to give workers representation on company boards could be misguided," he added.