(WARSAW) - Seventy-five percent of Poles would ratify the EU's reforming Lisbon Treaty in a referendum should Poland's parliament fail to muster the required two-thirds majority vote, a survey said Monday.

Relegated to the opposition in a snap election last October, Poland's eurosceptic ex-prime minister Jaroslaw Kaczynski has threatened to torpedo the Lisbon treaty in parliament.

This has prompted the new liberal Prime Minister Donald Tusk to moot the possibility of putting it to a referendum.

Just seven percent of respondents to a survey by the independent Warsaw-based OBOP-TNS pollsters said they would reject the treaty, while 18 percent said they had no opinion.

The survey was conducted March 14-15 on a random representative sample of 1,000 voting-age Poles.

In Poland the treaty must be ratified either by parliament or a referendum before President Lech Kaczynski, former premier Jaroslaw Kaczynski's identical twin brother, can give it a final seal of approval.

Jaroslaw Kaczynski's conservative-nationalist Law and Justice party has demanded that the ratification legislation include wording banning future amendments to the treaty.

It also wants a guarantee on the supremacy of Poland's constitution and its sovereignty.

The Law and Justice party's votes are needed to ratify the treaty, because Tusk's government lacks the necessary two-third parliamentary majority.

A minimum 50 percent voter turnout is necessary for a referendum result to be valid. Sixty-seven percent of poll respondents said they would take part if a national vote was called.

Poland's parliament is due on Tuesday to resume a debate on the Lisbon Treaty.

Tusk had agreed that Warsaw would continue to refuse to sign the EU charter of fundamental rights, which the Kaczynskis oppose, in exchange for parliamentary ratification of the treaty.

Signed by EU leaders in December, the accord replaces the bloc's defunct draft constitution, abandoned after French and Dutch voters rejected it in separate referenda in 2005.

All 27 EU member states must individually ratify the wide-ranging text for it to come into effect, as planned, next year.

Last month France became the first EU heavyweight to approve the Lisbon Treaty by parliamentary vote.

Lawmakers in Hungary, Malta, Romania and Slovenia have also given their seal of approval.

Ireland is the only EU member to have announced plans for a referendum.

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