Dutch voters have overwhelmingly rejected the EU Constitution in a national referendum.

Provisional final results showed 61.6% of voters in the Netherlands rejected the treaty, with only 38.4% in favour. Turnout was reported to be 62.4%.

Unlike the French referendum, the Dutch vote was non-binding but the main parties said they would follow the will of the people if the turnout exceeded 30%.

Dutch Prime Minister, Jan Peter Balkenende, said he was 'disappointed' by the result but promised to honour the outcome.

The result deepens the crisis in the bloc further following the rejection of the constitution in France.

The rejection of the charter by the Netherlands - one of the six countries that founded the bloc in the 1950s - could deliver a fatal blow to the treaty.

It also casts doubt on the EU's hopes for a more muscular foreign policy and its plans to expand further to the Western Balkans, Turkey and Ukraine.

Prime Minister Jean-Claude Juncker of Luxembourg, the European Union President, said ratification of the constitution must continue in other countries despite rejection by Dutch and French voters.

The Taoiseach, Bertie Ahern, is to discuss the matter when he meets Mr Juncker and Chancellor Gerhard Schroeder of Germany tomorrow.

Reacting to the result, European Commission President Jose Manuel Barroso admitted the Dutch rejection heralded difficult times ahead for the EU.

The Dutch 'No' campaign was an unlikely coalition of right-wing and far left groups - each of which had different reasons for opposing the constitution.

Some talked of a loss of Dutch identity, anger over inflation thought to be brought on by the euro and opposition to Turkey's application to join the EU.

'Yes' campaigners argued that the constitution set out clearly the limits of what Brussels should do and strengthens Europe's role in a world dominated by the US and the rising strength of India and China.