"Yesterday's shining heroes of Brexit have become the sorrowful heroes of today," the European Commission president told the European Parliament as he condemned what he said was a lack of planning in London following last month's referendum, Reuters writes.
"They are retro-nationalists, not patriots. Patriots don't abandon ship when the going gets tough. They stay on board," Reuters quoted Juncker as saying.
Juncker insisted the EU will not negotiate any terms for the British departure until a new premier formally triggers the withdrawal process and the two-year deadline it sets for a deal.
"I would have thought that they would have had a plan," he said.
"Instead of developing a plan they are leaving the boat."
Former London mayor Johnson shocked his Conservative party by abandoning a leadership bid that many expected him to make to become prime minister. Farage, a European Parliament member whose seat in the Strasbourg chamber was empty on Tuesday, resigned on Monday as leader of the UK Independence Party, according to the report.
Speaking for UKIP during the debate, Paul Nuttall, a potential successor to Farage, told Juncker, "I'm not here to gloat", and said that Brussels and London must now cooperate to ensure the best deal for Britain and the rest of the Union.