WARSAW, Oct 8 (Reuters) - A Polish court ruling challenging the supremacy of European Union law plunged the EU into an existential crisis on Friday, increasing fears among EU policymakers and many Poles that Poland could eventually leave the bloc. Politicians across Europe voiced dismay at the ruling by Poland"s Constitutional Tribunal on Thursday that parts of EU law are incompatible with the Polish constitution, undermining the legal pillar on which the 27-nation EU stands. Ursula von der Leyen, President of the European Commission, said she was "deeply concerned" and that the EU executive she leads would do all in its power to ensure the primacy of EU law. She said in a statement that the EU"s 450 million citizens and its businesses need legal certainty, and the Commission would carry out a swift analysis to decide its next steps."We have to state clearly that this government in Poland is playing with fire," Luxembourg"s minister for foreign affairs, Jean Asselborn, said on arrival for a meeting of EU ministers in Luxembourg. "The primacy of European law is essential for the integration of Europe and living together in Europe. If this principle is broken, Europe as we know it, as it has been built with the Rome treaties, will cease to exist." Poland may have to consider the economic risks of its clash with the EU because until the issue is resolved, it is unlikely to see any of the 23 billion euros ($26.61 billion) in EU grants and 34 billion in cheap loans that it could otherwise count on as part of the EU"s recovery fund after the COVID-19 pandemic. The EU could even raise doubts about Polish access to EU grants for cohesion and structural projects in the 2021-2027 budget worth several times the recovery package, on the grounds that a country that rejects EU law cannot guarantee that the funds are spent as agreed, free of fraud. "If European legal acts are no longer accepted, it is questionable whether Poland can still profit from the enormous amounts of EU funding it currently receives," said Monika Hohlmeier, a member of the European Parliament from the centre-right group of the European People"s Party. "POLEXIT"Poland"s ruling nationalist Law and Justice party (PiS) says it has no plans for a "Polexit" and - unlike Britain before its Brexit referendum in 2016 - popular support for membership of the EU remains high in Poland. Poland"s membership since 2004 has helped drive some of the fastest economic growth in Europe. With an increasingly assertive Russia unnerving some central and eastern European states that were for decades under Communist rule, many Poles see the EU as an essential part of national security. But, welcoming the court ruling, Polish Prime Minister Mateusz Morawiecki said each member state must be treated with respect and the EU should not be only "a grouping of those who are equal and more equal." Right-wing populist governments in Poland and Hungary have found themselves increasingly at odds with the European Commission over issues ranging from LGBT rights to judicial independence. Poland"s Constitutional Tribunal took on the case after Morawiecki asked it whether EU institutions could stop Poland reorganising its judiciary. However, a Eurobarometer survey carried out in June and July 2021 showed that almost twice as many Poles trust the EU as trust their own national government. "I think...there is a risk that we could exit the EU, because all of these actions which are happening can lead to that, step by step," said Warsaw pensioner Grazyna Gulbinowicz. "I think it would have a very negative impact on our overall situation, because things are not easy and without EU funds it will be even more difficult, not to mention the fact that we will feel isolated." ($1 = 3.9872 zlotys) ($1 = 0.8643 euros)