The Dutch public appears on course to firmly reject the European constitution in a referendum on 1 June, according to latest opinion polls.
Support for the Dutch government has plummeted
A poll for RTL television indicated 54% would vote "No", with 27% voting "Yes".
The Dutch vote is purely consultative, but politicians have said they will take the result into consideration when it comes to a parliamentary vote.
The referendum comes only three days after one in France, where the "No" campaign has a slight lead.
A poll by Centerdata, also published on Thursday, showed 50.9% against the constitution and 28.6% for it.
Prime Minister Jan Peter Balkenende played down the latest polls, saying "I am putting my money on the 'yes' vote, I am optimistic," in an interview with De Volkskrant newspaper.
Dutch Socialist MP Harry van Bommel, a leader of the "No" campaign, told the BBC News website that the No leads in France and the Netherlands were helping encourage each other.
He said the influence and sovereignty of smaller EU member states such as the Netherlands would be severely threatened by the constitution, which is designed for the enlarged EU of 25 states.
The Netherlands is one of the EU's founding members, and support for the bloc has traditionally been strong among the Dutch.
However, tensions over immigration and the high financial cost of EU membership have led to increasing Dutch euroscepticism ahead of the poll.
Other factors pushing voters into the No camp appear to be the speed of European integration and opposition to Mr Balkenende's centre-right government.
Return to sender
In the TNS-NIPO conducted for RTL television, 90% of respondents said European integration, such as the EU expansion from 15 to 25 countries last May, was going too fast.
The main political parties, including the ruling Christian Democrats, say they will take the result into account if turnout exceeds 30%. The TNS-NIPO poll suggested a turnout of about 38%.
A similar poll in March suggested 38% intended to vote "No", while a foreign ministry poll in April showed 52% would support the constitution, with only 30% opposing it.
The Dutch Socialist Party has called on voters to return the government's referendum promotional material to the foreign affairs ministry marked "unwanted post".
Some far-right parties are also campaigning for a "No" vote.
The referendum must be approved by all 25 members to take effect. A "No" in France and the Netherlands would be a serious blow to the EU.
But senior EU leaders pushing for a "Yes" vote in referendums insist there will be no renegotiation of the treaty.
Mr Van Bommel also said Dutch people were being pushed towards a "No" vote because of the "ghost stories" being told by the government.
"The justice minister has even said there is a chance of war in Europe if there is a "No" vote - referring to the break-up of the former republic of Yugoslavia.
"The people in this country sometimes are not completely informed about what is going on, but they are not stupid. They are angry at the government for the fact that they are insulting their intelligence."