Angela Merkel on Thursday warned that Europe risks a “return to nationalism” if it does not secure its external borders, as polls showed support for the far-Right is rising in Germany amid growing fears of Islam.

“The future of Europe is at stake,” the German chancellor said in a passionate plea to preserve freedom of movement and the Schengen Agreement on border-free travel within the continent.

Even as she spoke, a new poll released on Thursday showed support for the far-Right Alternative for Germany(AfD) party is at its highest ever.

“Europe stretches from the North Pole to the Mediterranean. We must defend the Schengen Treaty and the external borders, or we risk a return to nationalism,” Mrs Merkel said.

She was speaking at a joint press conference in Rome with Matteo Renzi, the Italian prime minister.

Both leaders spoke out against plans by Austria to close its border with Italy at the Brenner Pass, to prevent migrants entering.

The AfD is riding high in the German polls on a wave of public discontent over the migrant crisis, and recorded its highest ever support less than a week after it adopted an anti-Muslim manifesto.

It is now in third place on 15 per cent, just five points behind Mrs Merkel’s main coalition partner, the centre-left Social Democrats (SPD), who have slipped to 20 per cent.