In a careful speech that pushed a centrist but conservative line, Dr Merkel reassured her CDU party conference that 2015's extraordinary refugee influx "can and must not repeat itself".

More than a million people have sought asylum in Germany since the summer of 2015. Since then European countries have closed their internal borders to migrants, preventing the movement of asylum seekers north from Greece and Italy.

But Dr Merkel also defended her refugee-friendly position, saying "every single" asylum application would be reviewed, though not all would end up able to stay.

She said the CDU stood for respecting the dignity of all people, regardless of ethnicity, gender or sexuality. And she took aim at those spreading hate speech and intolerance.

"All of our people determine who the German people are, not just the few, no matter how loud they may be," Dr Merkel said: a line interpreted as an attack on right-wing populists. It drew loud applause.

The CDU, and Merkel, are polling steadily ahead of the election, in defiance of a continent-wide trend to nationalist, right-wing populism. However even Germany is not immune and the CDU wants to inoculate against pre-election discontent.

Dr Merkel admitted "many people feel as though the world is coming apart at the seams", but insisted there was "no returning to the world before globalisation", telling the conference "it's rarely the simple answers that advance our country".

But she confirmed "the full-face veil is not acceptable in our country… It should be banned wherever legally possible."

Germany's constitution protects freedom of religious expression, and Dr Merkel's language reflected a debate within her party as to how far the government can and should go.

In August she rejected a push for a full burqa ban from senior ministers in her government – sending them back to the drawing board with instructions to draw up a more limited law.

The end result is still under discussion but is expected to cover courtrooms, government buildings, schools and public demonstrations. The fine for breaches is expected to be quite low.

Former UKIP leader – and Time magazine's person of the year shortlister - Nigel Farage commented that Dr Merkel's move was "too late – the horse has bolted".

In November Dutch MPs voted overwhelmingly to ban face-covering masks on public transport and in schools, hospitals and other public buildings. Those caught wearing masks can be fined up to 400 euros.

The law – which is yet to pass the country's upper house - also covers ski masks and helmets, but it is clearly aimed at Islamic veils such as the niqab and burqa.

The Dutch far-right Freedom Party, which is stridently anti-Islam and wants a full burqa ban, is polling strongly in advance of the country's elections next March,

France introduced a burqa ban in 2011, leading to more than 1500 arrests though only a handful of prosecutions.

The European Court of Human Rights ruled in 2014 that France's ban on full-face veils was consistent with the "values of an open democratic society", though it warned such a law risked "encouraging expressions of intolerance".

Belgium introduced a partial burqa ban in 2011, and Switzerland has a similar law in the works, and one region where it already applies.

Bulgaria introduced a new law this year where those covering their face in public can be fined more than 700 euros (100 euros for a first offence).

Norway has also announced plans to ban face-covering veils in schools and universities.

Dr Merkel, who ran unopposed for her party leadership, won the support of 89.5 per cent of members – down from 96.7 per cent two years ago.

The result was interpreted as minor embarrassment for the leader, and a reminder that she does not have the free hand that she enjoyed before the migration wave, and recent terror attacks.