Average pensions for top directors have increased to almost £260,000 a year, 25 times those of other employees, according to a new study.
Research among almost 300 directors in 100 FTSE companies found the average pension pot increased by £41,000 to £4.7 million.
The TUC said bosses continued to enjoy "platinum-plated" pensions, with most still able to retire at 60.
More directors are moving to defined contribution pensions, enjoying a "sharp increase" in employer contributions, said the report.
The union organisation said top bosses were finding new ways of rewarding themselves rather than showing any restraint on their remuneration packages.
TUC general secretary Frances O'Grady said: "Britain's top bosses already enjoy a level of pay and bonuses beyond common decency.
"But not content with grabbing an ever larger slice of the UK's earnings pie, they are adding to the country's growing inequality with their platinum-plated pensions.
"As pensions are not performance-related, there can be no justification for this stark divide in company pensions. Some directors are collecting millions while schemes are scaled back for ordinary staff."