New research suggests the average UK download speed fell to 4.9Mb during the final quarter of 2011.
The latest State of the Internet report from Akamai has pointed to a 0.2Mb fall in average speeds since Q3 2011.
Globally, average download speeds fell from 2.7Mb in the three months to September to 2.3Mb in the three months to December.
Akamai suggested that the fall in average internet speeds was "unusual", and a "fairly significant" development.
South Korea remained the number one country for download speeds, with consumers receiving an average of 17.5Mb.
Japan and Hong Kong tied for second place in the chart (9.1Mb), ahead of the Netherlands (8.2Mb), Latvia (7.8Mb) and Switzerland (7.3Mb).
The average download speeds reported by Akamai for the UK differ somewhat from those reported by Ofcom in February.
According to the communications regulator, the average speeds enjoyed by UK consumers stood at 7.6Mb in November 2011.