Denmark's border controls 'insufficiently justified', says commission

EU experts were "unable to get sufficient justifications from the Danish side for the intensification of the controls at the internal borders," said EU home affairs commissioner Cecilia Malmstrom in a statement.

The commissioner also warned that she would "not hesitate to use all tools" to ensure that EU law guaranteeing the free movement of peoples, goods and services is upheld.

An EU source explained that all border checks need to be based on risk assessment. An increased incidence of stolen cars could justify more car checks. Information on a human trafficking ring could justify checks on lorries. But such checks need to be detailed in a report specifying what was found.

The Danish customs officials have "no books" on what they are checking and when, the source said. Malmstrom has asked for this in a letter sent to the Danish authorities and warned she wants "regular information" from Copenhagen, while not ruling out "further visits".

Reacting to the commission's criticism, Danish foreign minister Lene Espersen said: "It is very important for Danish authorities to answer all the outstanding questions, but this is for the ministry of finance and the customs authority to do. We will respect all our obligations under the Schengen code and EU law."

She also added that that there have been "a lot of misunderstanding" surrounding the issue.

The escalating dispute has much wider symbolic importance than the face value question of whether Copenhagen is violating an EU law.

Re-instating controls at an internal border undermines the EU's Schengen Agreement allowing passport free travel in most of the EU's 27 member states, widely considered, along with the euro, to be one of the most far-reaching integrative steps in the bloc's history.

Copenhagen justified its move by saying that the open borders was facilitating crime but the border checks were widely seen as a quid pro quo deal with the populist Danish People's Party, whose support was necessary to secure a key reform to the pensions system.

Denmark's unilateral decision came at the height of a wider discussion on whether the EU needed to reform the Schengen rules, prompted by a dispute between Rome and Paris over Tunisian migrants making their way from Italy to France.

Pressed by Italian leader Silvio Berlusconi and his French counterpart Nicolas Sarkozy, EU leaders in June agreed the rules needed to be changed to allow as a "very last resort" the reintroduction of border controls in "truly critical" situations.

The commission has been tasked to come up with proposals in this political and legal minefield in September, but the Polish EU presidency is already looking at ways to strengthen the external border so as to "avoid by any means" the re-establishment of internal borders.