National borders are the "worst invention ever," the head of the European Union (EU)'s executive arm said on Monday, at a time when many countries in the bloc are looking to strengthen borders following terrorist attacks and a surge in refugee and immigrant numbers.
In a speech at the European Forum Alpach in Vienna, EU Commission President Jean-Claude Juncker said solidarity must be shown to refugees and their children.
"Borders are the worst invention ever made by politicians," he added.
His comments were quickly shot down by new U.K. Prime Minister Theresa May.
"This is not something the Prime Minister would agree with … The British people think that borders are important, having more control over our borders is important, and that is an issue we need to address," a spokesperson for May said, according to media reports.
Germany has reinforced controls at its border with Switzerland, Swiss finance minister Ueli Maurer said on Sunday, according to media reports. This follows a surge in the number of migrants crossing through Switzerland and a tightening in controls at the Swiss-Italy border.
The number of Syrian refugees in Europe continues to rise, but remains low compared to numbers in neighboring countries like Turkey. Over 1 million Syrians made asylum applications in Europe in the five years to June 2016, according to data from the United Nations.
Following several Islamist terror attacks in France, French President Francois Hollande has stressed the need for EU nations to tighten borders and share intelligence.
"To have security we need frontiers that are controlled, so that is why we are working to reinforce coastguards and border guards," he said on Monday, according to media reports, following a meeting with his German and Italian counterparts in Italy.
In an interview with CNBC on Tuesday, Carsten Nickel, senior vice president at political risk consultancy Teneo Intelligence, said he saw no move to loosen borders in Europe in the near-term. He added that the contrast between Juncker's opinions and political leaders' moves to tighten borders demonstrated that power in Europe lay with national politicians rather than EU bureaucrats.
"It goes to show that governments are firmly in charge of this process when it comes to managing the migration crisis. That of course hasn't always been helpful from a technical perspective, but again, politically I think it goes to show that all these leaders are massively constrained," he told CNBC from Brussels on Tuesday.