Europe’s leaders need to send a much stronger message that they will no longer offer “refuge and support” to migrants if they want to curb the right-wing populism spreading across the Continent, Hillary Clinton warned in an interview published Thursday.

Clinton said that while the decision of some nations to welcome migrants was admirable, it had opened the door to political turmoil, the rise of the right and Britain’s decision to withdraw from the European Union.

“I think Europe needs to get a handle on migration because that is what lit the flame,” Clinton said in the interview with the Guardian, which was conducted before the U.S. midterm election this month.

“I admire the very generous and compassionate approaches that were taken particularly by leaders like Angela Merkel, but I think it is fair to say Europe has done its part, and must send a very clear message — ‘we are not going to be able to continue provide refuge and support’ — because if we don’t deal with the migration issue it will continue to roil the body politic,” she said.

The European Union has struggled to come up with a comprehensive policy on migration in the wake of an influx of refugees and migrants that, in 2015 alone, brought more than 1 million people into Europe.

The many strains of coping with the sheer volume of new arrivals has caused crisis in many countries. Anti-immigration candidates have risen to power in Italy and Austria, and they have gained seats in countries like Germany.

The open migration policies of Merkel, Germany’s chancellor, ended up causing turmoil within her government and contributed to major electoral setbacks. She recently announced that she would step down as the leader of her conservative party in December and not seek re-election in 2021.

Democrats in the United States have also struggled to come up with a collective stance on immigration to counter President Donald Trump’s relentless focus on the issue.

In the run up to the midterm elections, Trump and his aides managed to overcome a steady stream of negative headlines about the brutal killing of a dissident by his close ally, Saudi Arabia, by shifting attention to a large caravan of Central Americans traveling toward the southern border of the United States.

After the publication of Clinton’s comments, some officials and academics denounced her criticism of European migration policies, saying they reflected the mentality of the very populists she criticized.

David Lammy, a member of British Parliament, urged politicians to “stand not against migrants, but in unapologetic solidarity with them,” in a tweet sent Thursday afternoon.

Tanja Bueltmann, a history professor at Britain’s Northumbria University who focuses on migration issues, countered Clinton’s claims in a tweet.

“Giving in to that populism, as you regrettably propose here, is exactly the opposite of what we should do,” she wrote.