Foreign Secretary William Hague has issued a blunt warning to countries like China and Russia to halt hostile cyber attacks on other states.
In his closing address to the two-day London cyberspace conference, Mr Hague said governments needed to realise that such online offensives were not in their interests.
His comments came after David Cameron told the conference that online attempts to steal state secrets were taking place on an "industrial scale".
"State-sponsored attacks are not in the interests of any country long-term, and that those governments that perpetrate them need to bring them under control," Mr Hague said.
He later told the closing press conference he was not going to publicly name the "guilty men" responsible for such attacks, which have in the past targeted the Foreign Office's IT system.
But earlier this week, former security minister Baroness Neville-Jones, who is now the Prime Minister's representative to business on cyber security, said Beijing and Moscow were "certainly" involved in that sort of activity.
"We are going about this in a diplomatic way," Mr Hague said. "We have and we will have I expect ever more so in the future on current trends vigorous private discussions about these things, particularly as our ability to detect cyber attacks and sometimes the source of them improves.
"It hasn't been our approach in this conference to identify countries and try to name and shame them. Of course that may happen on other occasions."
Mr Hague insisted there was "overwhelming support" among the 60 nations represented at the conference for the principle that the internet should remain open to the "free flow of ideas, information and expression".
He acknowledged that China and Russia, which advocate tighter regulation through a code of conduct, took a different view - one, which he predicted, would ultimately fail.