Average earnings of chief executives of FTSE 100 companies decreased by 17% last year, but a huge gap remains between bosses and workers outside the boardroom.

A FTSE 100 CEO typically received an average pay package – including salary, bonuses, incentives and employer pension contributions – of £4.5m ($6m) in 2016, according to research done by CIPD and the High Pay Centre think tank.

This compared to average annual earnings of £5.4m in 2015.

The decline in 2016 was brought about due to political pressure, public disapproval and campaigning, although Stefan Stern, director of the High Pay Centre, said that it may be a one-off.

The think tank said rewards at the top were still "extraordinarily high," with 60 of the FTSE 100 bosses being paid 100 times the typical annual pay of a UK worker, which currently stands at £28,000.

"We have finally seen a fall in executive pay this year, in the context of political pressure and in the spotlight of hostile public opinion," Stern said.

"This is welcome, but the response has been limited and very late. It is also, so far, a one-off.

"We need to see continued efforts to restrain and reverse excess at the top."

The study found the pay ratio between chief executives and their employees was 129:1 last year – meaning for every £1 paid to the worker, the CEO received £129. In 2015, the ratio was 148:1.

CIPD chief executive Peter Cheese said: "We have to hope that the reversal in rising executive pay is the beginning of a re-think on how CEOs are rewarded, rather than a short-term reaction to political pressure.

"The fall in executive pay is a step in the right direction, but it's still happening within an overall reward system where average wages in the UK have been flat."

The study also revealed stark disparity in gender pay, with female chief executives receiving an average pay packet of £2.6m in 2016 compared to £4.7m for their male peers.

WPP's Sir Martin Sorrell was by far the highest earning boss in the UK last year, taking home £48.1m.