Michael Howard has urged Welsh Tories to sign a petition calling for a referendum on the EU constitution.
Mid-June is the deadline for sealing a deal on the constitution
The Conservative leader will also publish Labour's telephone number as part of a poster campaign in the run up to June's European elections.
Mr Howard says Tony Blair should let the people decide whether Britain should adopt the new EU constitution.
"I believe that any proposal for a new constitution must be put to the British people in a referendum," he said.
Addressing Tory delegates during the party's conference in Llandudno, he said: "Whatever your view you should have a say."
"When it comes to transferring power to Brussels Tony Blair says 'trust me'. Conservatives say 'trust the people'."
The Tories have already indicated that calls for a referendum on the EU constitution will be a central plank in their Euro election strategy.
At a Conservative-initiated debate earlier this week, shadow foreign secretary Michael Ancram said his party would use "every parliamentary device" to stop Mr Blair from railroading through an EU constitution.
He argued that Labour had no mandate for the measure as it was not in the party's manifesto.
But Mr Blair said he wanted agreement on the constitution "as quickly as possible".
The prime minister said he would not surrender sovereignty on the key "red line" issues of tax, foreign policy, defence or the criminal justice system.
But the Tories have argued the constitution would give the EU "many of the trappings of statehood", including a president, a foreign minister and
a new legal status.
Mr Ancram said: "Tony Blair keeps saying he wants to have a big conversation with the country but he is completely ignoring them over one of the biggest issues facing us today.
"The European Constitution will lead to a substantial transfer of power away from Britain to the EU.
"It is a very important decision and people are entitled to have their say in a referendum.
"Over the next months, we will campaign to increase the pressure on Tony Blair and force him to listen.
"The prime minister expects everyone to trust him, but he has got to learn to trust the people."