The UK has slipped from 31st to 35th place in the global broadband league tables, behind 25 other European countries, research suggests.
Analysis of 163 million broadband speed tests across 200 countries indicates Singapore ranks as the world's fastest country, with Yemen the slowest.
Average speeds in the UK have gone up in the past year and, at 18.5Mbps, are above the global average.
Globally, average speeds have risen from 7.4Mbps to 9.10Mbps.
The data was collected by M-Lab, a partnership between Google Open Source Research and Princeton University's PlantLab, and the results compiled by UK broadband comparison site Cable.
The UK's ranking - while above 165 other countries - puts it in the bottom third of EU member states.
Fastest broadband speeds can be found in:
- Singapore - average 60Mbps
- Sweden - 46Mbps
- Denmark - 43.9Mbps
- Norway - 40.1Mbps
- Romania - 38.6Mbps
- Belgium - 36.7Mbps
- Netherlands - 35.9Mbps
- Luxembourg - 35.1Mbps
- Hungary - 34Mbps
- Jersey - 30.9Mbps
The slowest 10 nations are:
- Yemen - 0.3Mbps
- East Timor - 0.49Mbps
- Turkmenistan - 0.56Mbps
- Somalia - 0.6Mbps
- Guinea 0- 0.65Mbps
- Mauritania - 0.7Mbps
- Syria - 0.8Mbps
- Niger - 0.83Mbps
- Burkina Faso - 0.84Mbps
- Republic of Congo - 0.85Mbps
Cable's consumer telecoms analyst, Dan Howdle, said it was "somewhat sad to see the UK not faring better".
"A number of other countries have leapfrogged us since last year, including France and Madagascar," he said.
"Compared with many other countries both in and out of Europe, the UK has simply come too late to a full-fibre solution.
"Despite plans to roll out full fibre to UK homes across the next decade or so, the UK is likely to fall further behind while we wait."
More to do
In a report published on the same day, the UK government's National Infrastructure Commission (Nic) has called for full-fibre broadband to be deployed around the UK by 2033, and to be available to 15 million homes by 2025.
Full-fibre - known as FTTP (fibre to the premises) - has previously been rejected as too costly for large-scale rollouts by UK infrastructure provider Openreach.
Instead, many homes rely on the slower FTTC (fibre to the cabinet), which uses copper wires to carry broadband from street cabinets to homes.
Rivals to Openreach are rolling out faster services in cities around the UK. Hyperoptic plans to offer FTTP to 2 million urban premises by 2022, while Cityfibre aims to reach 1 million by 2021.
Openreach is still owned by BT but in November 2016 was ordered by regulator Ofcom to become a legally separate company, in part because of its slowness to deploy super-fast broadband.
It acknowledged there was "more to do".
"We are in the process of hiring 3,500 engineers to support us with the rollout of ultrafast fibre to 3 million more people by 2020," a spokesman told the BBC.
While the speeds in the UK were not the best, there were other measurements - such as availability and speed - where the UK would fare better, said Matthew Howett, principal analyst at research company Assembly.
"Some countries are also of course easier to roll out broadband in. The fastest country in this survey, Singapore, is about the size of London and obviously doesn't have the same challenges with remote and rural areas that we have in Britain," he said.
"Encouragingly, Britain is set for more fibre, with leading operators and their competitors all having committed to deploy so called full-fibre.
"Once those deployments ramp up, they would be reflected in similar league tables."