By Marcin Goclowski and Pawel Florkiewicz


WARSAW (Reuters) - Poland's centrist opposition said on Tuesday it will maintain its near month-long blockade of parliament's main hall if the ruling party tries to launch a new session this week, deepening a standoff over media rights and the budget vote.


The Civic Platform (PO) and the liberal Nowoczesna, Poland's largest opposition groups, began protesting against the ruling Law and Justice (PiS) party's plan to curb media access to parliament by occupying the speakers' podium in mid-December.


The spat has only intensified after the ruling party held a vote on the 2017 budget in a side room, sidestepping the opposition' blockade. Opposition lawmakers say the vote was illegal and are demanding a rerun.


The PiS's actions provoked popular protests in Warsaw last month and drew a rebuke from the European Commission, which expressed concerns over what it called a continued "systemic threat to the rule of law" by the eurosceptic government.


The next parliamentary session is due to begin on Wednesday. Grzegorz Schetyna, leader of the PO, said they would lift the blockade if parliament's speaker resumed December's session and returned to the budget vote.

If ruling lawmakers insisted the budget vote was legal and tried to open the next parliamentary session then Schetyna said the opposition would occupy "any room in which they will try to organize proceedings".

The PO party says it was not clear the ruling party had enough lawmakers present to validate its budget vote - an assertion dismissed by PiS leader Jaroslaw Kaczynski who told journalists on Tuesday that was sufficient support.

The 2017 budget envisages a higher fiscal deficit than last year - though still under the European Union-imposed cap of 3 percent of national output - and the opposition says the PiS is risking long-term prudence with higher welfare spending.

Earlier on Tuesday Kaczynski appeared to offer a compromise. He said his party proposed that the Senate pass some opposition amendments and then send the budget bill back to the lower house of parliament, where the PiS also has a majority.

"We could even consider an adoption of some of these amendments, provided they do not totally ruin the budget," Kaczynski told the state-controlled TVP1 television channel.

But the opposition's Schetyna said that was not enough.

"We need to respect the constitution and the rule of law," he said.

Despite attracting condemnation at home and abroad for what critics call the party's drift towards authoritarian rule, the PiS remains strong in Poland.

(Additional reporting by Agnieszka Barteczko, Anna Koper, Jakub Iglewski, Pawel Sobczak and Lidia Kelly; Writing by Lidia Kelly; Editing by Richard Lough)