Spammers living in The Netherlands could face a €1m fine.
This emerged from a European Commission study into counter-measures against online criminals published last week.
The study of more than 140 enforcement cases from 22 member states showed most cases were reported in Spain (39), Slovakia (39) and Romania (20). The highest fines were imposed in the Netherlands (€1m), Italy (€570,000) and Spain (€30,000).
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Communications commissioner Viviane Reding called to European member states to cooperate more to defeat spammers and other online menaces.
She noted that European law had prohibited spam and spyware since 2002, but on average 65% of EU citizens still receive regular spam, one in six from the US, according to security firm Sophos.
Reding called for clearer and more consistent enforcement rules and sanctions, better cross-border cooperation, and more resources for national privacy regulators. The EU's new telecoms rules now being finalised in the European Parliament would help, she said.
The new rules would also let national spam fighters join the European network of authorities that enforce consumer protection laws. Private organisations such as internet service providers will be entitled to take legal action against spammers that abuse their networks, she said.
She added the commission was negotiating with the US on cross-border cooperation in the enforcement of consumer protection laws to stop spammers.
Reding said there are already cooperation agreements in Belgium, Cyprus, Estonia, France, Germany, Italy, Latvia, Lithuania, the Netherlands, Romania and the UK. Luxembourg and Malta rely on informal cooperation.