Brussels has threatened to launch legal proceedings against France for failing to implement EU laws on the free circulation of people, standing its ground in the ongoing standoff over France's Roma deportations.
Paris was given until 15 October to respond.
"The right of every EU citizen to free movement within the Union is one of the fundamental principles of the EU," the Commission said in a statement.
"At this stage, the Commission considers that France has not yet transposed the Directive on Free Movement into national legislation."
A letter of formal notice will be sent to France requesting the full transposition of the directive, "unless draft transposition measures and a detailed transposition schedule are provided by 15 October 2010".
France is also being asked detailed questions regarding the practical application of its repatriation policy since this summer and to explain in particular that it "did not have the objective or the effect of targeting a specific ethnic minority, but treated all EU citizens in the same manner".
It is not yet clear whether the October deadline applies to that particular aspect of France's repatriation policy, which is at the centre of the current standoff.
France singled out
It had earlier been expected that the warning to Paris would be issued alongside a raft of similar proceedings against a dozen other countries, including Italy, where popular resentment against the Roma has been running high (EurActiv 21/05/08).
But in the end, France was singled out, signalling that the Commission has no intention of giving up on the issue, which has triggered a heated exchange between French President Nicolas Sarkozy and Commission President José Manuel Barroso at a European summit two weeks ago (EurActiv 17/09/10).
In a statement, the French foreign ministry said that "France, like the other member states, will bring the necessary elements to complete [the Commission's] evaluation".
The statement said "France takes note that no procedure has been started" regarding the conformity of its legislation with EU laws on the free movement of people.
Speaking before the French National Assembly in Paris, French immigration minister Eric Besson told MPs: "We should all be happy. France is emerging with its head high from its exchange with the Commission. It's good news for everyone."
Taking the honours of the hemicycle
Meanwhile, EU Justice Commissioner Viviane Reding was visibly received with great satisfaction by the European Parliament in the large hemicycle where plenary sessions usually take place.
Reding made clear that Europe had changed under the Lisbon Treaty and the Commission had new powers which it intended to use.
"I think the Parliament has understood very well that the decision of today to open infringement proceedings against France, on this very important basic question on values and rights, was a very strong movement," the commissioner said.
"And here you have the whole commissioners' college behind this infringement proceeding, just saying 'no, we cannot accept that essential procedural safeguards, rights for the European citizens, not even speaking about the Roma, rights for European citizens have not been put into national law, and thus could not be used in order to protect citizens in a crisis situation," she elaborated.
Touching upon the discrimination aspect, she cited the administrative memo from the French administration dated 5 August, which she said clearly violated EU law. This circular was corrected on 13 September, "but what has happened in between?" she asked.
"On this, we do not have concrete answers and concrete proof," she said.
Legal procedure not excluded
"We do not have the legal proof in order to go in front of the court on the discrimination [account]. We say very clearly that the assurances which have been given by the French authorities are very positive sentences, but we need to verify the facts. And this is why the Commission sent this letter to the French government, asking for very clear information about very clear facts," Reding said.
She then listed the relevant documents which the Commission was expecting from the French authorities, citing "the copies of the orders of expulsions" sent to Roma families.
"And we need not one or two, we need wide numbers in order to go ahead with this analysis," she said.
"We haven't closed any files, the file is on the table. And we are giving until 15 October to the French autority to respond to these very very concrete questions."
Roma strategy due in 2011
In the longer term, the Commission announced it will present an EU Framework for National Roma Integration Strategies in April next year.
The strategy will assess the use of national and European funding and make proposals for more effective implementation of EU funds in tackling Roma exclusion.
Member states are invited to present their own strategies for the inclusion of Roma as part of national reform programmes to be submitted under the 'Europe 2020' targets on poverty reduction, employment and education.