“Europe is a garden,” Mr Borrell said in a speech in Belgium, but “most of the rest of the world is a jungle, and the jungle could invade the garden”.
Mr Borrell's analogy was meant to persuade rookie diplomats that Europe should seek alliances to avoid hostilities with the outside world.
But critics said his speech smacked of racism and imperialism and reflected long-outdated views of European superiority.
“This analogy is terribly offensive. It has strong colonialist and racist undertones,” said Philippe Marliere, an expert on French and European politics at University College London.
Dionis Cenusa, a political risk analyst and researcher for the Eastern Europe Studies Centre, said Mr Borrell should apologise in the EU's name for his latest remarks.
Mr Borrell said in his speech on Thursday: “Europe is a garden. We have built a garden. Everything works. It is the best combination of political freedom, economic prosperity and social cohesion that humankind has been able to build — the three things together.
“The rest of the world [is] not exactly a garden. Most of the rest of the world is a jungle, and the jungle could invade the garden.
“The gardeners should take care of it, but they will not protect the garden by building walls. A nice small garden surrounded by high walls in order to prevent the jungle from coming in is not going to be a solution. Because the jungle has a strong growth capacity, and the wall will never be high enough in order to protect the garden.
“The gardeners have to go to the jungle. Europeans have to be much more engaged with the rest of the world. Otherwise, the rest of the world will invade us, by different ways and means.”
Russian officials saw an opening to lash out at perceived western arrogance and imperialism, a favourite Kremlin theme.
“The 'garden' was built by Europe due to the barbaric attitude to the plundering of the 'jungle',” said Russian Foreign Ministry spokeswoman Maria Zakharova.
Ahmed Shaheed, a former UN special rapporteur, suggested diplomats should read the Joseph Conrad novel Heart of Darkness, a critique of western imperialism in Africa.
It was the second time in a week that a speech by Mr Borrell raised eyebrows. On Monday, he lashed out at the EU's own diplomatic corps for failing to give him timely briefings.
“I want to be informed by you, not by the press. Sometimes, I knew more of what was happening somewhere by reading the newspapers than reading your reports,” he informed EU ambassadors.
In the same speech, he admitted the EU had dismissed US warnings in February that an invasion of Ukraine was imminent.