The Lisbon Treaty, if passed, will change the Czech Republic's international position and may reduce its sovereignty, President Vaclav Klaus told the Constitutional Court on Tuesday.
The European Union (EU)'s reform treaty is at variance with the spirit of the Constitution and its "material core," Klaus said.
The treaty will push the EU closer to a federal state, Klaus said.
Klaus called on the judges to be free of political pressure when making their decision and to realize the weight of their verdict, reported Xinhua.
"The decision on the Lisbon treaty will not be valid for today and a few next years, but we will be bound by it for a number of next generations," Klaus said.
Klaus said at the close of his speech that the court should rule that the treaty is at variance with Czech law.
He voiced the view that if there are any doubts about harmony with the constitutional order, the court should decide against the Lisbon Treaty.
The treaty, Klaus said, will also limit the powers of the court.
"The Lisbon Treaty has started a process at the end of which the EU will be the sovereign that will order its rules not only to individual EU members, but also to their citizens," Klaus said.
EU bodies will have the power to limit the sovereignty of EU members, Klaus said.
Irish voters rejected the reform treaty in a June referendum.
The Constitutional Court is considering the question of whether the treaty is compatible with the Czech Constitution.
The Czech Republic is the only EU state not to have taken an official position on the treaty so far.
The Czech Republic will hold the EU presidency from January. Enditem