German Chancellor Angela Merkel is paying a high political price for spearheading a European Union deal with Turkey aimed at stemming the flow of refugees from the Middle East to Germany and northern Europe.

The deal, which is based on Ankara taking back refugees arriving in Greece from Turkey, has sparked widespread criticism across Europe with the agreement seen as providing Turkey’s autocratic president Recep Tayyip Erdogan with leverage over the EU.

The result has been to send Ms Merkel’s poll numbers tumbling, while placing at risk her authority as Europe’s pre-eminent political leader amid increasing concerns the refugee deal could unravel.

The agreement with Ankara faces a crucial test this week when Brussels considers a key part of the accord, which calls for the EU to grant 78 million Turkish citizens visa-free travel in the EU from June.

'The issue of the visa waiver is vital for Turkey,' Turkish Prime Minister Ahmet Davutoglu said at a joint news conference earlier this month with Merkel and top European officials during a trip to Turkey aimed at easing tensions over the deal.

The number of migrants making the perilous journey across the Aegean Sea from Turkey to Greece has dropped sharply since March when Ankara and the EU signed the deal, which also involves reviving Ankara’s long-stalled EU accession talks and providing Turkey with €6 billion ($9 billion) in EU aid to arrange refuge for the 2.7 million migrants stranded in the nation.

But the plan for sending asylum seekers back to Turkey has not been fully implemented as a result of concerns expressed by groups including the UN and European humanitarian organisations about a range of issues, notably the treatment of non-Syrian refugees. Ankara does not apply the Geneva Convention on refugees in full. 

Resistance to the visa waiver is also running high in both Ms Merkel’s conservative, Christian Democrat-led bloc and several EU member states. Those opposed fear the move would pave the way for a new wave of Muslim migration into Western Europe, which is already battling its biggest refugee crisis since the Second World War.

Among the sceptics is Berlin’s number one ally, France, where French President Francois Hollande faces a tough reelection fight in the first half of next year.

But then it was tensions unleashed by the arrival last year in Germany of more than one million refugees fleeing wars in the Middle East and Africa that forced Ms Merkel to agree to Turkey’s requests —  to speed up its EU accession talks and obtain the visa waiver — so as to stanch the flow of asylum seekers.

Turkey’s political leadership might have distanced themselves from last week’s comments from the Turkish parliament speaker, Ismail Kahraman calling for the nation’s constitution to reflect its Islamic identity.

Still, for many in Western Europe, Mr Kahraman’s remarks have only added to worries about the sense of change underway in Turkey.

'The introduction of Islam as a state religion would result in further divisions in Turkey’s already highly polarised Turkish society and threaten social peace,' said Cem Ozdemir, co-chairman of the German political party Alliance '90/The Greens, who is of Turkish origins.

But even before Brussels decides whether to grant Turkey the visa waiver, German prosecutors could rule on whether a German comedian should face criminal charges as a result of a crude poem he read out on public TV about Mr Erdogan, which the Turkish leader claimed insulted him.

A decision by prosecutors that the comedian, Jan Boehmermann, has a case to answer, could pile on the pressure on Ms Merkel's after she agreed to allow prosecutors to consider the issue, sparking a bitter row in Germany about free speech and artistic freedom.

Mr Erdogan had demanded Mr Boehmermann face charges under an antiquated law, which prohibits insults against foreign leaders and which has been untouched since the 19th century when slights of honour could settled by drawing pistols at dawn. 

The Boehmermann case and the EU refugee deal have come just as Ankara’s human rights record and its crackdown on the media — along with reports of a black list of foreign journalists — have helped to fuel worries that Turkey is increasingly out of step with western European values. 

Ms Merkel herself has in the past been one of the prominent opponents of Turkey’s long-held quest for EU membership.

But her decision in the Boehmermann case has left her open to claims that she has allowed Mr Erdogan to export his clampdown on freedom of speech to Europe. 

Up until recently, Ms Merkel’s personal approval ratings have remained remarkably high despite the concerns about the refugee crisis and a sharp slump support for her conservative Christian Democrat-led political bloc in the wake of a deep split among her supporters about her handling of the migrant drama.  

If Ankara meets its side of the bargain, the EU has promised to recommend on Wednesday that EU states approve visa-free travel for Turks. A recent Politbarometer poll suggested 80% of Germans believed the chancellor had made too many concessions to Turkey in her negotiations with Ankara over the refugee crisis.

Most doubted that Ankara is a reliable partner, while 62% of those polled said they were deeply unhappy with the chancellor's decision to ask prosecutors to rule whether Mr Boehmermann had case to answer for.

Ms Merkel has already announced that the section of the criminal code which Mr Erdogan had taken his legal action would be removed by 2018.

But the sudden plunge in her support appears to have rattled the chancellor who has acknowledged she made mistakes in the handling of the Boehmermann case, a rare admission for a political leader.

Her description of Mr Boehmermann's satirical poem — which implied the Turkish leader enjoyed child pornography and had sex with animals, among other insults — as 'purposefully offensive' could have given the incorrect impression that freedom of opinion and of the press were no longer important to her, Ms Merkel said.

'With hindsight that was a mistake,' she said attempting to set the record straight ahead of a visit to a refugee camp in Turkey and a meeting with Turkish Premier Ahmet Davutoglu.

Human rights and values would always feature in diplomatic discussions, 'but human rights, rights to freedom, the rights of the press are indispensable assets,' Ms Merkel said.

'And that a situation can arise where it is thought that such things would be abandoned because we just made a deal with Turkey — that was flawed,' she said.

Photo: Dan Kitwood/Getty Images