Donald Tusk has claimed external powers meddled in the Brexit vote as he called for EU member states to do more to protect the upcoming European elections.

Speaking at a press conference in Brussels with the Armenian prime minister, Nikol Pashinyan, the European council president said he agreed with the French president, Emmanuel Macron, who used a column in the Guardian and other newspapers to call on European countries to be alert to malign influences.

“There are external anti-European forces, which are seeking – openly or secretly – to influence the democratic choices of Europeans, as was the case with Brexit and a number of election campaigns across Europe. And it may again be the case with the European elections in May,” said Tusk, a former prime minister of Poland and vociferous critic of Vladimir Putin.

Tusk’s intervention echoed fears Russia sought to foment anti-EU sentiment during the 2016 EU referendum campaign in the UK.

Following an inquiry into the dissemination of disinformation, a select committee of the British parliament last month called for the government to urgently examine the impact of foreign powers on the result of that vote.

Tusk urged those who supported the EU to be vigilant for signs of interference. “Do not allow political parties that are funded by external forces, hostile to Europe, to decide on key priorities for the EU, and the new leadership of European institutions,” he said.

“We cannot wait for the renaissance of Europe – the renaissance of Europe must start now.”

The European commission is pushing social media companies to do more to deal with disinformation, and has recently criticised Facebook, Google and Twitter for failing to live up to its obligations under a voluntary new code of conduct.

Officials have said there has been “patchy” data passed on to Brussels about the platforms’ efforts to disrupt revenue for accounts and websites misrepresenting information, clamp down on fake accounts and bots, give prominence to reliable sources of news and improve the transparency of funding of political advertising.

Meanwhile, the Brexit secretary, Stephen Barclay, and the attorney general, Geoffrey Cox, are dining with the EU’s chief Brexit negotiator on Tuesday evening, after their latest talks.

The UK is seeking legally binding assurances that the customs union envisaged in the Irish backstop will be only be temporary if it were to come into force.

Barclay has also formally asked the commission to preserve the citizens’ rights section of the withdrawal agreement whatever the outcome of the negotiations, following a vote in the House of Commons in favour of the proposal.

The commission has so far refused to negotiate “mini-deals”, claiming they would suggest the Brexit talks had failed.

Arriving in Brussels, Cox declined to comment on the “details” of his talks. Asked whether there was sufficient time before the Commons vote next week to secure the assurances he is seeking, Cox said: “There is always hope”.

“There are reasonable conversations going on,” he added. “These are very sensitive discussions. I think that we’re having very constructive dialogue at the moment”.

Asked to comment on speculation that the prime minister might visit Brussels on Sunday to sign off on any legal work, Cox told reporters: ‘Wait and see”.