Theresa May will urge EU leaders meeting in Brussels to create a new sanctions regime to crack down on governments found responsible for cyber-attacks.

Amid growing fears about Russian meddling in foreign elections, including in Europe, and attempted cyber-attacks, most recently on the chemical weapons watchdog in the Netherlands, the prime minister will call on her fellow leaders to take tougher action.

“Individual efforts to protect ourselves, and to call out irresponsible behaviour, are not enough,” she is expected to say. “Malign cyber activity causes harm to our economies, and undermines our democracies. As well as protecting ourselves against attack, we must impose proportionate consequences on those who would do us harm.”

“We should accelerate work on EU restrictive measures to respond to and deter cyber-attacks, including a robust sanctions regime.”

May is keen to underline the fact that Britain will continue to co-operate closely with the EU on security matters after Brexit next March.

She has repeatedly highlighted the malign influence of Russia on global stability, including in a strongly worded Mansion House speech in March, when she warned president Putin: “We know what you are doing. And you will not succeed”.

EU member-states joined Britain this year in a concerted diplomatic response to the poisoning of Sergei Skripal in Salisbury – an attack now believed to have been carried out by officers of the Russian intelligence service, the GRU.

The prime minister will attend the regular meetings of the European council in Brussels on Thursday, after talks about Brexit on Wednesday night.

Her intervention follows the decision by EU foreign ministers to adopt new sanctions against chemical weapons attacks, at the foreign affairs council in Luxembourg on Monday.

“I believe that we have an opportunity to show our collective political leadership,” May will say. “We have demonstrated significant steps forward against other challenging threats. And should today make clear that malicious cyber activities are no different; we will impose costs on all those who seek to attack us, regardless of the means they use to do so.”

The Dutch and British governments published details this month of an attempted Russian cyber-attack on the international chemical weapons watchdog, the OPCW.

The incident, which was thwarted with the help of British intelligence officials, came after the Sandworm cybercrime unit of the GRU had attempted unsuccessfully to hack the UK Foreign Office in March and the Porton Down chemical weapons facility in April.

EU leaders, including May, will call for action to combat “cyber-enabled illegal and malicious activities” before the European elections in May 2019, according to a draft summit communiqué.

The EU wants to finalise a number of cyber security laws before the final session of the European parliament in April, including a plan to prevent dissemination of terrorist content online.

The EU’s security commissioner, Julian King, has also warned social media companies that they could face regulation without voluntary action to prevent a repeat of scandals such as when Facebook data was harvested without users’ permission to secretly target them with political ads.

The leaders will call on the commission to assess how a voluntary code for social media companies is working by the end of the year. Measures to combat “unlawful data manipulation and fighting disinformation campaigns … deserve rapid follow-up by the competent authorities,” the draft communique states.