European Commission President Jean-Claude Juncker has lashed out at Brexit campaigners Boris Johnson and Nigel Farage for "leaving the boat" after winning the referendum vote on withdrawal from the EU.
Addressing the European Parliament in Strasbourg, Mr Juncker said Mr Johnson, who has pulled out of the Tory leadership race, and Mr Farage, who quit as Ukip leader, were "not patriots".
He accused the two "sad Brexit heroes" of walking away the moment things became difficult and said he could not understand why the Leave camp did not have a properly worked-out plan for pulling out of the EU.
"The Brexit heroes of yesterday are now the sad Brexit heroes of today. Those who have contributed to the decision in the UK have resigned - Johnson, Farage and others," he said.
"They are, as it were, retro-nationalists. They're not patriots. Patriots don't resign when things get difficult - they stay."
He strongly criticised calls from some on the Leave side to delay invoking Article 50 - which triggers the start of the formal two-year withdrawal process - warning there would be "no negotiation before notification".
"I could understand why the Remain camp needs weeks to reflect but I don't understand that the Brexit camp needs months before knowing what to do," he said.
"I would have thought they would have had a plan. Instead of developing a plan, they are leaving the boat."
He said that if Britain wanted to continue to have free access to the EU single market it would have to accept the free movement of labour.