By Lidia Kelly and Pawel Sobczak
WARSAW (Reuters) - Poland remains fully committed to the European Union despite a series of bruising battles with Brussels and any political party that advocated following Britain out of the bloc would be rejected by Polish voters, President Andrzej Duda told Reuters.
The EU, which Poland joined in 2004, has sharply criticized Poland's ruling right-wing Law and Justice party (PiS) over its reforms of the constitutional court, state media and other measures, saying they undermine the rule of law.
This month Poland was further isolated in the EU after it tried in vain to block the reappointment of Donald Tusk, a former Polish prime minister and arch rival of PiS leader Jaroslaw Kaczynski, as chairman of the European Council.
Polish Prime Minister Beata Szydlo has also said Warsaw might refuse on Saturday to endorse a declaration in Rome to mark the EU's 60th anniversary unless its concerns over the bloc's future course are properly addressed. On Friday she softened that stance before taking off for Rome.
President Duda, an ally of Kaczynski and Szydlo, said Poland only wanted to be treated as a fully equal partner in the EU and that there was no question of Poland leaving the bloc.
"Today any party which came out and openly said 'We are a group ... that is striving to quit the EU, we don't want Poland in the EU' would have no chance on the Polish political scene," Duda said in an interview authorized for publication on Friday.
"We want a Union of free and equal nation states."
Poland is the largest beneficiary of EU funds and is due to receive 77.6 billion euros ($83.82 billion) in the current 2014-20 budgetary period for infrastructure projects, its poorer regions and improving the competitiveness of its economy.
SUPPORT FOR EU MEMBERSHIP
Opinion polls suggest up to 80 percent of Poles back membership, though many are also opposed to deeper EU integration, immigration and joining the euro currency.
"Anyone who knows the Polish situation and history since 1989 (the fall of communism) understands how important it was for us to join the EU and how much we have gained," Duda said.
"Not just in purely financial terms or in terms of living standards or infrastructure, but also in terms of what we call a 'freedom' - the freedom to move around, without borders."
PiS, a socially conservative and eurosceptic party which also favours higher social spending to help poorer Poles, swept to power in late 2015, ousting the EU-friendly, market-oriented Civic Platform that Tusk had led as premier from 2007 to 2014.
In the EU, PiS wants a bigger role for national parliaments - a stance similar to that of Britain, which will next week kickstart its EU divorce proceedings. Kaczynski told Prime Minister Theresa May in talks in London on Thursday that Poland regretted Britain's decision to leave the bloc.
But Warsaw has failed to garner enough support for amending the EU treaties to give greater weight to national parliaments.
Duda, a 44-year-old former lawyer and parliamentarian, said the proposals were "still on the table" but signalled Warsaw was ready to work "within the treaties" to achieve its aims.
PiS has also expressed concern over calls by Germany, France and Brussels for a 'multi-speed Europe' in which some states seeking closer integration could move ahead without waiting for the whole bloc. Poland fears this could create a two-tier EU.
Duda said EU member states were already able under existing rules to move ahead in certain areas if they wished to.
"Now, however, the notion is to create some exclusive clubs. This is a very bad tendency," he said.
In Poland, the government wields most power, but the president is commander-in-chief of the armed forces, has a say in foreign policy and limited veto powers over legislation.
(Writing by Lidia Kelly; Editing by Gareth Jones)