The analysis of internet traffic data over two years found that 95 per cent of the emails that went through ClearMyMail's anti-spam system via Force 9 and Talk Talk were spam or virus related.
"These are worrying statistics," said Dan Field, managing director of ClearMyMail.
"I was shocked when I saw some of the names in the top 10 which seem to take little or no action when it comes to preventing spam, and even more shocked to see that the UK is still the second biggest source of spam emails received in this country.
"ISPs, anti-spam and antivirus providers need to get together to see what can be done to eliminate the time consuming and frustrating spam emails that are increasing in numbers."
ClearMyMail also looked at which countries produce the highest number of UK-targeted spam emails. America led the way with just under 50 per cent of all spam coming from the US.
The nearest competitor is the UK, with 13 per cent of the total, followed by China, Germany and France all producing less than seven per cent of the spam targeted at the UK.
The US topping the list is not particularly surprising as it is known as a source of spam botnets, but other countries such as Russia do not feature on the top 10 list and Japan only comes in at number 10.
ClearMyMail top 10 most spammed ISPs by average spam rate:
1. Forece9.net - 95 per cent
2. Talk Talk - 95 per cent
3. UKServers - 94 per cent
4. Eclipse Internet - 92 per cent
5. Yahoo - 89 per cent
6. Orange (Wanadoo/Freeserve) - 89 per cent
7. PlusNet - 87 per cent
8. Zen Internet - 85 per cent
9. Demon - 84 per cent
10. Pipex - 84 per cent
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