Europol: Schengen enlargement will boost irregular migration

Even if the entry of the two countries would not "change the face of the earth," he stressed the need for risk assessments and other appropriate measures to be taken, especially since the Balkan region has seen the biggest increase in smuggling and human and drug trafficking in Europe in recent years.

His comments will add fuel to the debate whether Bulgaria and Romania should be given an entry date this year, after EU interior ministers postponed a decision on the move until after the summer break, awaiting more progress in the fight against corruption and organised crime.

Both countries had hoped to join the border-free area of 26 countries in 2012, but opposition from the Netherlands, France, Germany and a handful of other states with mounting domestic debates about immigration have hampered these plans.

A crackdown on corrupt border officials in Romania took place earlier this year in a bid to increase trust in its capacity to secure the Schengen frontier. Border police last week also arrested the wife of a diplomat from Congo after finding more than 18,000 cigarette packs hidden in her car.

"Using diplomatic immunity, the smugglers were bringing cigarettes to Romania at least twice a week," organised crime prosecutor Mircea Andres said during a press conference.

Meanwhile, in the Nordic countries - once a safe haven for refugees and irregular migrants - the anti-immigrant debate is heating up. The Finnish capital of Helsinki on Tuesday evacuated several Roma camps, following a decision by the city counci - a move similar to the French crackdown last summer.

Denmark, where the government had to give in to demands from the anti-immigrant People's Party when securing a vote on the pension reform - is also going ahead with increased customs controls on its borders.

Danish foreign minister Lene Espersen on Wednesday is expected to travel to Berlin in a bid to smooth over tensions with its southern neighbour over this controversial move. Meetings with the Swedish and the Polish foreign ministers are also scheduled in the coming days.

According to a statement on the Danish justice ministry's website: "The agreement implies a strengthening of policing in order to enable the Danish police to act upon specific requests from customs officers. However, this does not mean that the Danish police will be permanently present at the border."

Neither will passport controls be re-instated or individual checks of every single person crossing the border, the ministry says.

New customs control buildings will be built on the borders and "spot checks" will be carried out, however. Number plates will also be registered using video surveillance.