Danish Prime Minister Helle Thorning-Schmidt on Wednesday called a general election for June 18, as opinion polls show her centre-left coalition trailing an opposition bloc bolstered by the success of the far-right.

"Denmark is back on track, we are out of the crisis... It's time to ask the Danes if they want to maintain this direction," said Thorning-Schmidt, who under election regulations had to hold a vote by September 14.

"I want all of Denmark with (me). The growth must benefit everyone," she added.

A weighted average of five public opinion polls gives the opposition a lead of 6.5 percentage points over the government and its allies in parliament, according to news agency Ritzau.

The right-wing bloc, led by centre-right party Venstre, would need the support of the Danish People's Party (DPP) to pass legislation in parliament just like it did between 2001 and 2011, in return for which the anti-immigration party was allowed to shape Danish migration policies into some of Europe's toughest.

Some opinion polls have shown the DPP, which wants to tighten asylum rules further and raise public spending, garnering more votes than Venstre.

Support for the DPP has risen with the growing numbers of asylum seekers from Syria -- even though they remain relatively low compared to those received by neighbouring Sweden and Germany -- and fears that cheap labour from eastern Europe could undermine the Danish model of collective wage bargaining.

The party, which has been criticised for U-turning on key issues when public opinion changes, has not said whether it will seek to join a future coalition government. It disagrees with Venstre on Denmark's relationship with the EU and the level of public spending.

- Controversial moves -

Lars Loekke Rasmussen (R), pictured here in 2011 with Helle Thorning-Schmidt, was prime minister from 2009 to 2011 Keld Navntoft, Scanpix Denmark/AFP/File

Denmark was badly hit by the financial crisis of 2008, which caused the country's property bubble to burst.

Since taking office in 2011, Thorning-Schmidt's Social Democratic-led government has overseen a sluggish economic recovery that only recently began gathering pace.

On Tuesday, the government raised its economic growth forecast for 2015 to 1.7 percent from a previous estimate of 1.4 percent, and maintained a two-percent growth estimate for next year.

The 48-year-old prime minister, who is married to British Labour Party MP Stephen Kinnock, has been unpopular with voters for much of her tenure after implementing what many viewed as a right-wing programme.

Some of her more controversial moves have included cutting corporate taxes, rolling back unemployment benefits and selling part of state energy utility Dong to a US investment bank.

Thorning-Schmidt's handling of twin terrorist attacks by an Islamist gunman in Copenhagen in February boosted her popularity but failed to rub off on the parties that support her government in parliament.

Ahead of the election she has already pledged to spend more on welfare than opposition leader Lars Loekke Rasmussen, head of the Venstre party, which says it wants to improve public services without growing one of the world's most generous welfare states.

Rasmussen, who is unpopular with voters after a string of spending scandals, was prime minister from 2009 to 2011. He replaced Anders Fogh Rasmussen (no relation) when the latter was appointed secretary general of NATO.

In a bid to win back some of the working class voters who have left her party for the DPP, Thorning-Schmidt likened the opposition leader's plans to freeze welfare spending to an "experiment".

"The opposition wants a different path. Here each free krone will go to questionable tax cuts," she said.

Still, analysts said the election would have little impact on Denmark's economic recovery.

"One of the strengths of the Danish economy is that there is a high degree of consensus about economic policy," Sydbank economist Peter Bojsen Jakobsen wrote in a note to investors.

"We therefore do not expect the outcome of the election to have any significant effect on the development in the Danish economy," he added.