The Bank also said higher spending before a general election later this year may boost growth in the short run, but it would probably widen the budget deficit to 1.4 percent of gross domestic product this year and 1.6 percent in 2020, from 0.5 percent in 2018.
Poland's ruling Law and Justice party pledged last month to raise public spending by up to $10 billion a year, focusing on child subsidies, state pensions and transport infrastructure, as part of its election campaign.
"The Polish economy is still growing at a rate significantly above the EU average. The low unemployment rate and strong wage growth are still driving private consumption; investments, both public and private, are growing, too," Carlos Pinerua, the World Bank country manager for Poland and the Baltic States, said in a statement.
"We do expect, however, that Poland's fiscal situation may deteriorate soon," he said.