EU Council President Donald Tusk told European leaders Brexit resulted from the “failures” of British politicians, as he invited them to discuss the UK’s departure from the Union.
He said anti-EU politicians often launched attacks on Europe to cover up their own shortcomings, a sentiment echoed in stinging comments made by EU Commission President Jean-Claude Juncker.
It comes as leaders of 27 EU member states gathered in Slovakia to discuss the future direction of the bloc at a summit excluding Britain.
In a letter sent to leaders inviting them to the Bratislava meeting, Mr Tusk said the EU did have shortcomings and that it was sometimes justified to criticise it.
But he added that national leaders had a responsibility to the EU, saying: “It also means refraining from the constant accusations aimed at the Union, which sometimes are justified, but more often than not they serve as an easy excuse for one's own failures.
“This was also one of the reasons behind the Brexit vote.”
Europe's leaders face a difficult task plotting a way forward for the bloc, given internal divisions, a lack of clarity around the terms of Brexit and no clear indication on whether the country even intends to stay in the single market.
Despite some irritation, Theresa May has insisted she will not trigger Article 50, launching formal Brexit talks, before the end of the year.
There is the added difficulty for German Chancellor Angela Merkel and French President Francois Hollande who face crunch national elections in 2017.
Uncertainty over the pace, and scope, of Brexit was highlighted by former Council President Herman Van Rompuy, who said detailed withdrawal negotiations may not start until the end of 2017.
Mr Van Rompuy described the outcome of the EU referendum as a "political amputation".
In an interview, Mr Juncker claimed 40 years of "lies" were responsible for Britons deciding to leave the EU and that the result showed "something was wrong in Britain", as well as with the European project.
He said it was not surprising a majority were in favour of quitting the EU after being told repeatedly the Brussels-based organisation was "stupid".
The refugee crisis, counter-terrorism and tax regulation, are also set to be major issues at the summit.
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