The remarks against the Nord Stream project, which is also backed by Germany's E.ON Ruhrgas and BASF/Wintershall, came during the regional Council of Baltic Sea States, which kicked off Wednesday.
Several council states joined Poland at the conference in saying they would like to strengthen cooperation on economic projects in the region, but opposed the underwater Nord Stream, Deutsche Welle reported Thursday.
"We believe that the gas transfer by land would be cheaper and more effective," said Polish Prime Minister Donald Tusk, expressing his opposition to the 745-mile pipeline.
European ministers said in a May petitions committee report that while Nord Stream is "a project of European interest," they would "use every legal means at their disposal to prevent the construction" should it prove to pose a significant environmental risk.
Danish Prime Minister Anders Fogh Rasmussen backed those sentiments, saying the council supported reforms aimed at reducing the environmental impact of economic developments in the region.
Council members German Chancellor Angela Merkel and Russian Prime Minister Vladimir Putin chose not to attend the conference held in the Latvian capital, Riga.