Brexit campaigners Boris Johnson and Nigel Farage are "sad heroes" who are guilty of "leaving the boat" instead of developing a plan after standing down in the wake of the Brexit vote, according to Jean-Claude Juncker.
Farage yesterday resigned as leader of the UK Indepdence Party, while Boris Johnson ended up not running for the Conservative leadership after Michael Gove launched a surprise bid.
Juncker hit out at the two, telling the European Parliament: "The Brexit heroes of yesterday are now the sad heroes of today.
"Those who have contributed to the situation in the UK have resigned, Johnson, Farage and others. They are as it were retro-nationalists, they are not patriots. Patriots don't resign when things get difficult, they stay.
Juncker went on to condemn those who campaigned for Brexit without any conception of what would follow as Britain has failed to trigger Article 50 and thereby kick-start the process of leaving the EU.
Prime Minister David Cameron also announced that he would stand down from his post, thereby leaving his successor to trigger Article 50 and negotiate with the other 27-member states of the EU.
Read more: Boris Johnson's five point plan for Brexit
Also during the parliamentary session, President of the European Council Donald Tusk reiterated his hope that the UK and EU will continue to have close ties in the future, but added his warning that there would be no single market à la carte.
"We will not sell off our freedoms and there will be no single market 'a la carte'," he told MEPs.
He also said that the EU is ready to proceed with "an amicable divorce", but added: "We cannot effectively force this decision on the UK."