Donald Tusk, leader of the Polish Civic Platform (Platforma Obywatelska (PO) party speaks during a rally during an anti-government demonstration organized by the opposition in Warsaw on June 4, 2023. AFP
The announcement of the infringement procedure came despite Polish President Andrzej Duda saying last week he would propose amending the law on the panel after criticism from the EU's executive and the United States.
Commission Vice President Valdis Dombrovskis said the commission had "agreed to start an infringement procedure by sending a letter of formal notice" to Warsaw.
Poland, a neighbour and staunch ally of Ukraine, which is battling Russia's invasion, set up the committee with the stated goal of investigating citizens who may have succumbed to Russian influence.
Under the law, signed by Duda last week, those found guilty could find themselves banned for 10 years from public positions relating to public finances and classified information.
Critics, though, argue the measure, which the governing conservatives introduced just months before parliamentary elections, would be used to target opposition leader Donald Tusk.
His party has even gone so far as to dub it the "Lex Tusk", or Tusk Law, due to its suspected aim.
The European Union on Tuesday said it had "special concern" over the committee while the United States said the legislation "could be used to block the candidacy of opposition politicians without due process".
Duda on Friday said he had put forward an amendment that would do away with the penalties.
Instead, the committee would just issue a statement indicating that the person had succumbed to Russian influence and could not be guaranteed to properly work in the public interest.
Duda, who is allied with the governing conservatives, also proposed staffing the committee with experts instead of lawmakers or senators.
He called on parliament to adopt his amendment as soon as possible.
Poland's governing conservatives have been at loggerheads with Brussels since coming to power in 2015 over claims Warsaw fails to fully uphold EU laws particularly with regards to the judiciary.
Tusk, a former prime minister of Poland and European Council president, is posing a major challenge to the ruling Law and Justice party (PiS) ahead of elections later this year.
The head of the centrist opposition party Civic Platform (PO), he rallied half a million demonstrators in Warsaw last week in one of the largest anti-government protests since communism ended 30 years ago.