Why criticism of Turkey's crackdown could impact efforts to stem migrant crisis

• Video report by ITV News Middle East Correspondent Geraint Vincent

"Turkey is like a filter, holding back many things from Europe." So the governing party official told me in the Turkish port of Izmir, as another layer of politics enters the refugee crisis.

The EU and Turkey did a deal earlier this year. Turkey agreed to stem the flow of refugees in return for European financial support, and a promise of visa-free travel for Turks in Europe.

Then there was a coup attempt in Turkey, to which the government of President Tayep Erdogan responded by throwing tens of thousands of people in jail.

European criticism of the crackdown has grown ever louder, and the Turkish government doesn’t like it. After the European parliament voted in favour of suspending accession talks last week, President Erdogan threatened to reopen his borders.

What’s at stake in this stand-off is more human catastrophe. Officials in Izmir estimate that there are between 200 and 400 thousand refugees in the city. Eighty percent of them, they say, would go to Europe immediately, if they could.

It’s an hour-long boat journey from Izmir to the nearest Greek island of Cheos, which has become a holding pen for thousands of refugees, stuck between the sea and a European mainland which is doing its best to close down the migrant routes.

One of the camps on Cheos was the target of a firebomb attack last week, which was blamed on far-right extremists. The camps themselves are overflowing, with tents pitched on the beach by the harbour, flapping in a wind which is getting colder every day.

With a great deal of difficulty, crisis is being held at bay on these shores. Turkey might yet choose to give it a push.