Rasmussen, former prime minister and leader of the Liberals, the biggest opposition party, wants Denmark to get rid of its opt-outs on Defence and Justice via a "quick" referendum, possibly in May next year to coincide with the European elections.
Speaking in Norway earlier this month, Rasmussen put forward his demand, saying that he raised the question in private conversations with Thorning-Schmidt.
“The time has come; we need to deal with these opt-outs. The negative effects of especially the justice opt-out are so urgent that it would be irresponsible to keep pushing a referendum ahead. The condition is a broad support in Parliament and this is what I’m offering now,” Rasmussen told the daily Politiken.
Denmark currently has four opt-outs from common EU policies: security and defence; citizenship; freedom, security and justice; and the economic and monetary union.
Rasmussen proposed that the referendum could go alongside either the European Parliament elections in May 2014 or as part of a referendum on the EU patent court, which Denmark is likely to have at the beginning of next year. However, the liberal party leader does not want a referendum on the euro opt-out.
Danish Minister for Justice, Morten Bødskov, has often decried the disadvantages of Denmark's opt-out from Europol, the European law enforcement agency working on police cooperation.
While many EU member states are calling for closer cooperation, Denmark could risk being sidelined and decisively weakened in the fight against cross-border criminality, Bødskov argues.
In its work 2011 programme, the Danish government promised to hold a referendum on the two opt-outs during its first term. Since then Thorning-Schmidt has withdrawn the pledge.
While the prime minister and the newly-appointed European affairs minister, Nick Hækkerup, have refused to comment on the matter, Sofie Carsten Nielsen, the EU rapporteur of the Social Liberals, one of three parties in the Danish government, said the new signals were “enormously positive.”
“There is no one like the Social Liberals who are more interested in getting rid of the opt-outs. It’s extremely important for Denmark. It’s up to the prime minister to decide on the date. But we are interested. We are all ears to what Rasmussen is saying,” Nielsen said.
In parliament, Danish politicians are generally quite EU-friendly. But the widespread scepticism towards Europe among the Danish public makes it difficult for the government to carry out its ambition of getting closer to the EU's core, with any referendum on the matter likely to attract strong opposition.
Marlene Wind, a professor of EU studies at Copenhagen University, said Rasmussen’s announcement was "very important".
“This definitely moves a referendum on the opt-outs closer. We know that there has to be a broad support among the EU positive parties in order to get a positive outcome from the voters. A government can’t call for a referendum without clear backing from the opposition,” she said.