Brussels - The European Commission praised the accomplishments on Thursday of the EU single market, while calling on member states to show the "political courage" needed to whittle down remaining barriers to cross-border trade.

The report comes as Britain is preparing to leave the European Union and with it the single market, which offers free movement of people, goods, services and capital.

In practice, however, there are still numerous barriers to cross-border exchanges within the EU. The commission has put forward a range of proposals, for example to deepen the eurozone currency area and improve EU-wide standards.

But only a third of such measures put forward by the current commission have been adopted, it said in a statement. Some, such as the eurozone proposals, are highly contentious among member states.

"In a world where multilateralism is being challenged ... the single market is a unique asset to preserve and boost our continent's standing, values and influence in the world," said commission Vice President Jyrki Katainen.

"Just as we are resisting protectionism outside the EU, we should resist fragmentation inside the EU," added Internal Market Commissioner Elzbieta Bienkowska.

One key priority for the commission is to remove bottlenecks that could curb investment within the single market. This is a key goal of the so-called Juncker plan, an investment project improving access to finance for small and medium-sized companies.

Since its inception four years ago, the Juncker plan has boosted the EU's gross domestic product by 0.6 per cent, with that figure set to reach 1.3 per cent by 2020, the commission stated on Thursday.