STRASBOURG (Reuters) - The deputy head of the European Commission said a dispute with Warsaw over Poland's top court has not been resolved, while European lawmakers lambasted the EU's biggest ex-Communist state on Tuesday for undercutting democratic checks and balances.


Earlier this summer, the European Union executive gave Poland's nationalist-minded government until late October to reverse changes to the country's Constitutional Tribunal, which Brussels says go against democratic principles.


With U.S. and EU pressure piling up on Poland, Warsaw has since offered some concessions. But Commission deputy head Frans Timmermans told the European Parliament in Strasbourg on Tuesday: "At this stage, the dispute concerning the composition and the judgments of the constitutional of the tribunal remains unresolved."


Tensions between Warsaw and Brussels have grown steadily since the Law and Justice (PiS) party won elections a year ago, introducing a eurosceptic tone to foreign policy, defying Brussels and Berlin on migration and carrying out changes at home that critics say threaten the rule of law.


The PiS government says it has a strong public mandate to carry out reforms and accuses the main opposition, the pro-EU Civic Platform (PO), of undermining its own country abroad.


"This is not a debate against Poland but about the abuses of the current authorities that threaten democracy, rule of law and go against its own society," said Janusz Lewandowski, a PO member of the European Parliament told the chamber.

His parliamentary faction, the European People's Party, teamed up with four other groups to draft a resolution criticizing the Polish government for undermining democratic standards and values. The European legislature was due to adopt it on Wednesday.

The deepening dispute has tarnished Poland's reputation in the EU and has also bitterly divided the country of 38 million.

Speaking separately in Warsaw after talks with Poland's Prime Minister Beata Szydlo, European Council President Donald Tusk, formerly the head of PO and Poland's prime minister for seven years, told reporters: "A large part of Europe would want Poland to be a very reliable country again, including on the rule of law."

But PiS' own faction within the European Parliament and some other Polish lawmakers defended the government.

"The EU is going through the greatest crisis ... Brexit, a possible exit of other countries, lack of democratic standards, migration crisis. And now you are orchestrating a debate on Poland," said Ryszard Legutko, a PiS MEP.

"Why? I think because your political allies lost their monopoly on power and they can't get to terms with it."

There is little sign Poland will bow to the pressure and it is highly unlikely that the European Commission would be able to punish it directly with the maximum sanction foreseen in such cases -- stripping Warsaw of its voting rights in the EU.

Poland's souring ties with Brussels may backfire, however, as the bloc is reviewing its common budget and some EU states want to take funds away from Warsaw to punish the member state they increasingly see as a trouble-maker.

(Reporting by Alastair Macdonald and Gabriela Baczynska; Editing by Catherine Evans)