EU Commission President Jean-Claude Juncker made the announcement in his State of the Union address on 13 September. He said: “It is high time to bring Romania and Bulgaria into the Schengen Area.

“And incidentally Croatia too deserves full membership of the Schengen Area as soon as all of the criteria are met.

"All but two member states are duty bound to join the Euro area. These member states need the support of a euro accession instrument."

Of non-EU states, Iceland, Norway, Switzerland and Liechtenstein are also part of the Schengen Area.

Bulgaria and Romania were believed last April to have fulfilled the criteria to join Schengen, with the decision just needing to be rubber stamped.

Romania is due to take over the Presidency of the EU Council in 2019, and is thought they will be a fully fledged member by then.

The EU has monitored the two countries progress since they joined the bloc in 2007, in particular their judicial systems which were seen as open to corruption.

That same year, the Commission set up the Cooperation and Verification Mechanism (CVM), which gives both Balkan states benchmarks to set their progress against.