By Annabella Nielsen and Erik Matzen
COPENHAGEN (Reuters) - Denmark's mainstream parties, ruling and in opposition, are rushing to conclude an agreement governing their policies towards the European Union before an election next year in which a far-right Eurosceptic party is expected to make strong gains.
The Danish People's Party, which like others around Europe won strong support in May's elections to the European Parliament, said this week Denmark should hold a referendum on its EU membership if Britain went ahead with its own vote.
British Prime Minister David Cameron has promised his voters an in-out referendum on continued EU membership in 2017 if his ruling Conservative Party wins next year's UK election.
In response to the Danish People's Party pledge, larger Danish parties have said they want to forge a formal written agreement on EU-related issues.
Foreign Minister Martin Lidegaard from the Danish Social Liberal Party, a junior partner in the Social Democrat-led coalition government, said the Danish People's Party should be excluded from all decision-making on EU issues.
"The government is very interested in a new EU political agreement as soon as possible to create stability in Denmark's EU politics, preferably a long-term agreement covering both this election period and the next," Lidegaard told Reuters.
Earlier this week Prime Minister Helle Thorning-Schmidt called for a referendum on whether Denmark should adopt EU justice rules, from which Denmark - like Britain - has a legal "opt-out".
Along with Britain, Denmark is also the only member of the 28-nation EU with a legal opt-out from having to adopt the euro currency. Danes voted resoundingly against joining the euro in a 2000 referendum and remain opposed today.
LIBERAL PARTY SILENT
Lars Barfoed, spokesman on EU issues for the opposition Conservatives, said his party was also interested in joining the planned agreement.
"Such an agreement should of course include a referendum to remove Danish reservations about defense and police cooperation (with the EU). The question of the euro has to wait," he said.
However, the Danish People's Party may yet gain an influential voice at the table.
Opinion polls show the main opposition centre-right Liberal Party with the highest support ahead of the 2015 election, ahead of the governing Social Democrats, but with only 24 percent.
The Danish People's Party is now the third most popular party on 20 percent and the Liberals may yet need their support to form a new coalition government. The Liberals have declined to comment on whether they would join the EU policy agreement.
Mainstream political parties in Denmark, which joined the EU with Britain and Ireland in 1973, have had a decades-old tradition of striking cooperation agreements on EU policies.
But Danish People's Party leader Kristian Thulesen Dahl told Reuters the party would no longer toe the line.
"It is obvious that if David Cameron succeeds with a referendum on leaving or changing EU membership in 2017, Denmark should also have a similar referendum," Thulesen Dahl said.
Denmark's growing scepticism about the EU was on display in the European Parliament elections, when the Danish People's Party received the largest share of the vote with 26.6 percent, doubling their number of seats in the assembly to four.
"We just can't ignore the fact that so many people gave us their vote because of our EU scepticism," Thulesen Dahl said.
(Editing by Sabina Zawadzki and Gareth Jones)