Nevertheless, the political parties representing the majority in parliament have said they will respect the results if there is a high turnout.

The question Dutch voters will be invited to answer on 1 June will be: "Are you for or against the Netherlands agreeing to the treaty to establish a constitution for Europe?"

Negative sentiment increasing

The Netherlands is one of the founding members of the EU. However, recent Eurobarometer polls have shown it is one of the countries where negative EU sentiment is on the rise.

And a recent poll showed a majority in favour of the "no" campaign, with 29 percent in favour and 42 percent opposed.

Dutch politicians are less divided on the subject, as all the main political parties in the Netherlands support the Treaty.

Opponents include the leftist Socialist Party, two small Protestant parties, and the group of recently emerged populist politician Geert Wilders.

Nine other EU governments will hold a referendum on the Constitutional treaty, and 15 will ratify it by Parliamentary vote.

Spain's voters said a firm "yes" to the Constitution last Sunday (20 February), but the turnout was low (42.3 percent).

France and Luxembourg are due to hold referenda in the first half of 2005.

Hungary, Lithuania and Slovenia have already ratified the Constitution via their national parliaments.

The Constitution must be ratified by all 25 member states to come into force, the deadline being the end of October 2006.