Its assessment, it adds, can only begin once the 27 EU member states have agreed to a final deal on the treaty.

Portugal – the current holder of the rotating EU presidency – as well as the European Commission are hoping that the document's text will be finalised during an EU leaders summit in Lisbon on 18-19 October and officially introduced in 2009.

Legal experts in the Danish justice ministry will examine whether the reformed treaty represents any "delegation of powers" from the state to the EU – something that would automatically trigger the need for a referendum under the Nordic country's constitution.

If the experts conclude that the EU treaty does not represent a handover of power, then it becomes a political question of whether to hold a popular vote.

But Copenhagen – as with other member states – did as much as possible in the treaty negotiations to ensure that it will not have to have a poll.

It drew up a list of nine points which it said could no longer be included in the draft treaty if it was to avoid having a referendum. These points were then removed from the draft text.

Majority in favour of a referendum

A July opinion poll showed that more than half of voters (52.7%) wanted a referendum. The Danes had even scheduled a referendum on the EU Constitution in 2005 but cancelled it after France and the Netherlands voted no.

If the legal experts find that there is "delegation of powers" from Copenhagen to Brussels in the reform treaty, only a majority of five-sixths in the national assembly - the so-called Folketinget - can agree to the treaty without holding a referendum.

Morten Messerschmidt - the EU spokesman for the Danish People's Party says that as the EU is a facing a big restructuring of political power, then the population should be taken into consideration.

"When you wish to move so much power out of the member states then it is a condition that we can assure that the people are also willing to move all this power out of the countries. And that can only be secured with a referendum," Mr Messerschmidt told EUobserver.

His party has 23 seats in the 179-seat parliament and is a strategic partner of the governing Liberal and Conservative parties when pushing through new laws.

It is also the biggest group in the assembly wanting a referendum no matter what the outcome of the legal assessment.

Svend Auken, EU spokesperson from the Danish opposition party, the Social Democrats, argues that if the legal experts conclude that there is no handover of power, then there is no need for a referendum as it could have consequences for Europe.

He recently argued that a decision to have a referendum in Denmark could put pressure on the UK's Gordon Brown also to hold such a popular vote.

And if the Danes would vote no – as they initially did for the Maastricht Treaty in 1992 – then it would have a negative impact on European cooperation and Denmark's place in the EU.

So far, only Ireland has said it will definitely have a referendum. Other question mark countries were the Netherlands and the UK. The Dutch cabinet last week said it would not have a public poll while London is also resisting domestic political pressure to have one.