The UK dropped out of the top twelve spam relaying countries in the first quarter of this year, according to security firm Sophos.
Britain now accounts for 2.2% of messages caught by Sophos’ global anti-spam network, falling to 13th position from tenth in the first three months of 2006.
The US still holds top spot, with just under a fifth (19.8%) of the world's spam originating from US-based computers, the company said.
Poland – now lying in third place - is among the risers in the world league, with India also appearing in the top twelve for the first time.
Carole Theriault, senior security consultant at Sophos, said:
"The US stands out like a sore thumb in this dirty dozen. China, who until recently was an intimate rival to the US, dropped dramatically during the last quarter. Poland, on the other hand, has now gate-crashed the top three.
"Polish authorities would be wise to educate users on safe computing to ensure that they are not responsible for sending out massive gluts of spam."
The total volume of spam measured by Sophos rose by around 4.2% between Q1 2006 and 2007.
It said the quarter also saw it identifying the first pump-and-dump stock scam focusing on a company outside the US - Stonebridge Resources Exploration Ltd, which listed on the Frankfurt Stock Exchange on 1 March.
Mobile phone spam also appears to be growing, Theriault said:
"SMS spamming represents a handy new tactic for dodgy marketers - many people are used to ignoring unsolicited email spam, but they don't necessarily expect it to turn up on their mobile handsets.
"Instances of SMS abuse should always be reported to network providers, however it should be noted that while this type of spamming is on the increase, it still represents a tiny problem compared to email spam."