A showdown between the president and the prime minister has paralyzed the country as growth is set to slow. Business is starting to worry.

By Agnieszka Barteczko and Zosia Wanat Poland’s domestic cold war is escalating, posing a self-inflicted threat to Europe’s fastest-growing major economy.

Prime Minister Donald Tusk, 69, and President Karol Nawrocki, emboldened by Donald Trump’s support, have been locked in a bitter standoff since last year’s presidential ballot. A year before a general election, the confrontation has all but gutted the government’s agenda and prompted a rating-agency downgrade as efforts to narrow the budget deficit of more than 7% of GDP broke down. It now threatens to paralyze the central bank.

The conflict between pro-European Union liberals and nationalist conservatives has raged for years, but remained an economic non-factor: Gross domestic product doubled in the past decade to exceed $1 trillion, putting Poland among the 20 biggest global economies. Now, with energy prices soaring, Russia waging its own brand of warfare beyond neighboring Ukraine and the US fighting a global trade war, the crisis at the heart of Polish politics could put this track record in peril.

The economy is already slowing, with growth seen at 2.5% next year, down from 3.4% in 2026, according to the International Monetary Fund forecasts released this week, as inflows of EU funds slow and investments wane.

‘‘We are concerned that this conflict is escalating, especially given the high level of geopolitical uncertainty,’’ said Wojciech Kostrzewa, the president of the Polish Business Roundtable, a business lobby. ‘‘These are serious image issues for Poland, giving the impression of potential instability in the decision-making system.’’Poland’s rancorous politics have pitted the conservative Law and Justice party against the Civic Coalition for over two decades. Tusk’s return as the prime minister in 2023 after a two-term nationalist government marked by constant tensions with Brussels and rule-of-law concern had raised expectations the biggest of the bloc’s eastern members was again firmly anchored in the EU’s mainstream. Nawrocki’s come-from-behind victory in last year’s election shook the ruling coalition.

‘‘Businesses cannot plan investments around the ebb and flow of political disputes,’’ Joanna Makowiecka-Gatza, who heads Pracodawcy RP business lobby group, said, citing a gap in Polish corporate investments compared with an EU average, which would require an additional 300 billion zloty ($77 billion) annually to close.

Warsaw is no stranger to the divided government that the French call . Unlike in France, the Polish constitution sees the president as a largely ceremonial figure, but one who can veto legislation, heads the armed forces and also appoints judges, ambassadors and the central bank governor.

Nawrocki has tried to expand those powers to maximum effect. He has vetoed 45 pieces of legislation since taking office in August last year, more than double the number blocked by predecessor, Andrzej Duda, over two terms. The president has also refused to sign off on Tusk’s picks for ambassadors, leaving Poland without top diplomats in key capitals and leaving him the key interlocutor with Washington.

He has also drawn strength from his close relationship with Trump, who endorsed the little known former boxer with no previous political experience in the election, seeing him as a guarantor of Polish-US relations and an ideological ally.

It was during the election campaign that the seeds of the current feud were planted, making the conflict between Poland’s veteran politician and his 43-year-old right-wing rival deeply personal. Tusk publicly endorsed allegations that Nawrocki was involved in facilitating sex workers when he was a hotel security guard. The president has denied the claims and is suing the media outlet behind the story.

Earlier this year, Nawrocki unsuccessfully tried to block Poland from receiving its share of the EU’s €150 billion ($168 billion) loans-for-weapons program. Instead, he presented a plan together withcentral bank governor Adam Glapinski to use profit from gold reserves to fund defense.

The proposalinfuriated the prime minister and upset an agreement over candidates for the central bank’s management board, according to people familiar with the matter. Unless another deal is reached in the coming weeks, the number of board members would fall below the minimum six required by law, limiting the central bank’s ability to respond to any crisis situation at a time when bond markets are getting jumpy.

Last week, the ruling coalition also took a step toward suspending Glapinski, whom it has accused of doing the previous administration’s bidding ahead of the last parliamentary election. The governor has denied any wrongdoing and called the probe harmful for Poland. The central bank also warned the Monetary Policy Council, which sets interest rates, won’t be able to meet if Glapinski is suspended.

“We see these tensions everywhere,” said Maciej Gutowski, professor at the Faculty of Law and Administration at Adam Mickiewicz University in Poznan. “The constitutional principle of cooperation of powers certainly doesn’t work in Poland.”The cooperation between Nawrocki and the government ‘‘isn’t looking too good,’’ his spokesman Rafal Leskiewicz told Bloomberg. ‘‘It isn’t because the president doesn’t want it, but rather because the government isn’t supporting the president in his efforts’’ including those that would help Poland become a permanent member of the Group of 20, he said.

Government spokesman Adam Szlapka declined to comment.

The situation is even more strained in foreign policy as Europe’s east faces an increasingly bellicose Russia. Nawrocki has been trying to tap into growing anti-Ukrainian sentiment, stripping President Volodymyr Zelenskyy in June of the country’s highest state honor.

Just days after taking office, he unexpectedly vetoed legislation to extend aid for Ukrainians living in Poland, prompting warnings the decision would make it impossible for the government to pay for crucial Starlink satellite internet service used by Kyiv’s armed forces.

The breakdown of trust has only complicated talksthat Poland has been holding with Washington about setting up the US military base in western Polandafter Trump gave it a green light last year. The US president said last month the decision on what Nawrocki said would be called Fort Trump could come soon and praised his friend’s “bold leadership.”He also personally invited the president to the G20 summit in Miami later this year, a first for Poland.

Domestically, the prime minister’s response has been to escalate. Tusk has seen his agenda to reverse changes in the judiciary under the previous conservative administration torpedoed by the president. Appointing his policy aide to the to court, the prime minister has been blunt: “We won’t play chess with the hooligans. I’ve already been polite.”His scope is already limited. The government’s proposal to lower some taxes for the middle class, while increasing corporate taxes also depends on Nawrocki’s approval as the ruling coalition lacks the three-fifths majority in parliament to overturn his veto.

“All our efforts aimed at increasing the budget revenues, are sabotaged by the president,” Finance Minister Andrzej Domanski told Bloomberg last month. ‘‘Public finance is our common responsibility.’’Nawrocki has pledged ahead of the election that he won’t approve any tax increases. Asked about the standoff with the government, which Moody’s Ratings cited as one of the reasons for downgrading Poland’s investment-grade rating by one step to A3 last month, the president has been evasive.

“This is just a temporary problem of the Polish economy,” Nawrocki said in a Bloomberg TV interview in New York. “We are going to solve it in our home.”But he has already been forced to blink.

Earlier this month, the president unexpectedly reversed his position,ga bill introducing a windfall tax on fuel companies, clearing the way for a cap on prices at the pump. Nawrocki had stalled on the decision since July, but caved under pressure. Tusk couldn’t resist the rare opportunity to gloat.

In a social media postreleased on the morning after the decision, Tusk could be seen walking past the gate of the president’s neoclassical residence in downtown Warsaw. “There was no need to horse around like that,” the prime minister could be heard saying, tipping a cup of coffee in the direction of the building.