Britain's top bosses saw their pay cut to £4.5m last year, according to the High Pay Centre.
The thinktank, which analysed pay deals from 67% of FTSE 100 firms, revealed that the average pay packet fell from £4.9m ($8.2m, €6m) in 2012.
The research also revealed that the average "target" pay deal for chief executives among the country's top companies could drop further to £3.4m in 2014.
"Over the past 15 years, pay for a FTSE 100 chief executive has gone from being 60 times the average UK worker to 160 times, without any justification," said Deborah Hargreaves, director of the High Pay Centre.
"All workers should share in a company's success - our economy cannot succeed in the long-term if a tiny group at the top pull further and further away from everybody else."
WPP boss Sir Martin Sorrell topped the 2013 table after his pay surged by 70% to £29.8m, up from £17.5m in 2012.
The findings come despite new reforms from the UK government giving shareholders more power over executive remuneration packages.