European leaders are struggling to deal with the ramifications of the rejections, fearing the document may not survive.
Latvia needed two-thirds of its parliament to vote in favour of the text for it to be ratified, and 71 out of 100 did so.
The Baltic country’s constitution does not allow the EU basic law to be validated by a popular vote.
The ratification breathes new life into the constitution after it was broadsided when 55 percent of French voters voted against it, and an overwhelming 61 percent of Dutch voters followed suit.
European leaders insist the ratification of the EU constitution should continue despite the crushing defeats.
While admitting the overwhelming Dutch no vote meant “Europe no longer makes people dream”, EU leaders said the remaining members of the 25-nation bloc should continue the ratification process.
“Europe is not knocked down, we will do everything to ensure that it recovers very quickly,” said Luxembourg Prime Minister Jean-Claude Juncker, whose country holds the EU’s rotating presidency.
He acknowledged he was concerned about prospects for a referendum on the constitution in his own country, which is due to vote on July 10.
German Chancellor Gerhard Schroeder, a long-time partner with France in driving EU integration, also called for the voting to continue.
“Every member state has the right, and a duty, to go through its own vote. I am convinced that we need the constitution if we want a democratic, social-minded and strong Europe,” he said.
Unlike the earlier French referendum, the Dutch vote is non-binding, but the government promised to follow the will of the people.
Mr Balkenende is scheduled to attend a parliamentary debate on the outcome of the referendum on Thursday.
French President Jacques Chirac said the Dutch decision highlights people’s concerns over the EU’s direction, and must be considered at next month’s European summit in Brussels.
He also insisted the ratification process carry on regardless.
Poland says it would decide how and when to ratify the constitution after the EU summit. It had planned a referendum in October, but the opposition is demanding a delay.
But Britain, which assumes the EU presidency next month, took a more sceptical view.
“The prime minister and I have long made clear that the Constitutional Treaty is a good deal for Britain and for the EU,” said Foreign Secretary Jack Straw.
“But the verdict of these referendums now raises profound questions for all of us about the future direction of Europe.”
He avoided saying whether Britain would go ahead with its own plans to hold a referendum on the constitution in the first half of next year.
Nine European parliaments have voted in favour of the constitution, including Austria, Germany, Greece, Hungary, Lithuania, Slovakia and Slovenia. Spanish voters endorsed the text in a referendum.