Turkey is being handed the 'keys to the gates of Europe' through the deal with Brussels to tackle the migrant crisis, it was warned last night.

EU leaders are preparing to hand £4.7billion to Turkey and let its 77million citizens come to continental Europe without needing visas, in return for it taking back all migrants landing in Greece.

But opposition is growing to the plan with concerns that the Muslim nation's human rights record and treatment of refugees could make the plan illegal under European and international law.

Austria's interior minister Johanna Mikl-Leitner yesterday said she was 'extremely critical' of the deal with Turkey's president Recep Tayyip Erdogan.

EU leaders are preparing to offer Turkey (pictured, its president Recep Tayyip Erdogan) the deal in return for it taking back all migrants landing in Greece but critics have condemned the plan.

'I am seriously wondering whether we are taking ourselves and our values seriously or if we are throwing them overboard,' she said as she arrived for a meeting in Brussels.

At the European Parliament in Strasbourg, Guy Verhofstadt, leader of the liberals, said it was a 'deal to outsource our problems'.

'A deal in which we are giving in fact the entrance keys, the keys to the gates of Europe, in the hands of Turkey, of the successors of the Ottoman Empire, to Erdogan, I should even say maybe to Sultan Erdogan,' he added.

'He shall now decide on the entrance to the European Union.'

The EU has pursued the deal with President Erdogan despite the European Commission last year warning there had been a 'serious backsliding ' on human rights in a scathing report.

Officials in Brussels accused the government of undermining the judiciary and highlighted how journalists had had been prosecuted in criminal cases.

'Over the past year, significant shortcomings affected the independence of the judiciary as well as freedom of assembly and freedom of expression,' EU Enlargement Commissioner Johannes Hahn wrote.

The report, published in November, said Turkey's commitment to joining the EU was 'offset' by domestic actions that 'ran against European standards'.

It highlighted criminal cases against journalists and writers, intimidation of media outlets and changes to Internet law.

Leaders including David Cameron raised concerns with Turkish prime minister Ahmet Davutoglu about press freedoms during a lunch on Monday.

Last Friday Turkish police raided the offices of Zaman, a top-selling newspaper critical of the government.

Leaders including David Cameron raised concerns with Turkish prime minister Ahmet Davutoglu about press freedoms during a lunch on Monday.

Meanwhile fears were raised last night that migrants will attempt more difficult routes to get to Europe now the main trail from Greece into Macedonia has been closed.

Albania, which had previously been avoided because of its mountainous landscape, is making plans for a new flow of people, while Italy fears people might start trying to reach there across the Adriatic.

Turkey's EU affairs minister yesterday said the number of migrants they will take back would be 'thousands' rather than 'hundreds of thousands or millions'.

People who reach the Greek islands or are stopped in the Aegean Sea will be sent back to Turkey, but the deal will not apply to those already there.

The United Nations' human rights chief Zeid Ra'ad Al Hussein said: 'The EU's draft arrangement with Turkey... raises a number of very serious concerns, [including] the potential for collective and arbitrary expulsions, which are illegal.

'Border restrictions which do not permit determination of the circumstances of each individual violate international and European law.'

Under the deal, the EU would resettle one Syrian refugee directly from camps in Turkey, in exchange for every Syrian that Turkey takes back.

But Dutch migration minister Klaas Dijkhoff, whose country holds the six-month rotating presidency of the EU, said yesterday that it was 'not a permanent mechanism'.

'I think the one-on-one readmission and resettlement, it's temporary. I think when you have the one-on-one scheme, we will see over time that it won't pay off to cross the sea in an illegal and very dangerous fashion. So that flow will stop,' he said.

'And then we will have to talk with Turkey about a more permanent resettlement scheme in a sense of burden sharing.'