The UK has slipped from ninth to fourth place in Sophos' Dirty Dozen rankings for spam-relaying countries.
Of all the world's spam output from the second quarter of 2010, 4.6 per cent was sent from the UK, but this is less than a third of the 15.2 per cent that came from the US the country ranked number one on the list.
India was in second place with 7.7 per cent, while Brazil came in third on 5.5 per cent.
In continental terms, Europe is responsible for sending out the most amount of spam with 35 per cent, overtaking Asia which now lies in second with 30.9 per cent.
North America was far behind in third with 18.9 per cent.
"It's sad to see spam relayed via compromised European computers on the rise - the UK, France, Italy and Poland have all crept up the rankings since the start of the year," said Graham Cluley, senior technology consultant at Sophos.
"Spam will continue to be a global problem for as long as it makes money for the spammers. It makes commercial sense for the criminals to continue if even a tiny proportion of recipients clicks on the links."
Cluley urged businesses to adopt "a more proactive approach" to spam filtering and IT security in general so this global problem is not compounded.
The previous Dirty Dozen list for the first quarter of 2010 showed 3.1 per cent of global spam was relayed from within the UK, compared to 13.1 per cent from the US.
