Denmark remains 1st place for fifth year running in the Melbourne Mercer Global Pension Index (MMGPI) while the UK fell from 9th position in 2015 to 11th.
The MMGPI covered close to 60% of the world's population this year, measuring 27 systems against more than 40 indicators to gauge their adequacy, sustainability and integrity.
It warns that dramatically ageing populations, declining birth rates and a lack of robust retirement systems will see many countries struggle under the burden of providing adequate pensions without drastic action.
Mercer senior partner and report author, Dr David Know, said: "It is a political imperative that all countries, regardless of their size, and current standing on the MMGPI, implement the necessary policy changes to withstand future challenges presented by the globally ageing population."
The UK index value fell from 65.0 in 2015 to 60.1 in 2016, with Singapore and Ireland leapfrogging them in the table.
The reason for this fall was put primarily down to a reduction in the net replacement rate.
However the ongoing introduction of an auto-enrolment process is expected to improve the value in future years, broadening coverage and an increase in the level of funded retirement benefits.
The report suggests ways to increase the British system value:
Restoring the requirement to take part of retirement savings as an income stream
Raising the minimum pension for low-income pensioners
Further increasing the coverage of employees in occupational pension schemes
Increasing the level of contributions to occupational pension schemes
Raising the level of household saving
Accelerating the intended increases in the state pension age
Denmark scored an index value of 80.5, with the Netherlands (80.1), Australia (77.9), Finland (72.9) and Sweden (71.4) making up the top five.
Argentina had the lowest score on the index at 37.7, with Japan (43.2), India (43.4), Mexico (44.3) and China (45.2) all featuring in the bottom five.