While he personally believes "the EU will actually benefit from the youthful and rather well-educated Turkish labour force," Rehn admits some countries may view Turkey's EU accession differently.
"For instance in France, Turkish EU accession is seen through the lens of certain problems related to the integration of the Muslim minority: if you can call five or six million people in French society a minority, of whom only a small portion are Turks," Rehn said.
The commissioner does not have "much sympathy" for such attitudes, "because the EU is not a Christian club". But he acknowledged that something must be done to address such fears.
One instrument at the EU's disposal is the possibility of introducing measures to restrict labour movement, Rehn explained. "Concerning the free movement of workers, we may consider transitional periods and even permanent derogations," Rehn told EurActiv. "This is in order to alleviate fears among our citizens about problems related to the labour market and immigration."
He concedes that the question maybe empirical at this stage, as it is impossible to predict the circumstances in EU labour markets when Turkey eventually joins the EU, which is not expected to happen before 2015 at the earliest. But he said the Commission's Recommendation on Turkey's progress towards accession, published in October 2004, as well as the Negotiating Framework of 2005, both mentioned the possibility of "long transition periods" and "permanent safeguard clauses" to avoid disturbance in the EU labour market.
Such measures, if they are imposed, are likely to fuel resentment within Turkey. In December 2004, Recep Tayyip Erdogan, the Turkish prime minister, travelled to Brussels for a European summit which defined the conditions for launching accession negotiations with Turkey. His mandate stated that permanent derogations would never be accepted by his country.
Since then, the Union's representatives have been rather careful not to mention such clauses.
Responding to enquiries by EurActiv, Rehn said permanent derogations on the free movement of labour had never been applied by the Union before. "Not in this area," he said.
The full transcript of the extensive interview, during which the commissioner answered questions from the EurActiv network across eight EU countries as well as Turkey, will be published tomorrow (21 November).