"As far as I know, he's is not going (to run as candidate)," the party's member MP Leonardas Talmontas told BNS.
In his words, the decision was made during a meeting of the party's top leaders earlier this week.
The politician refused to comment on the causes behind the decision, adding that they should be given by Tomaševski himself. He could not be reached for comment on Wednesday.
On July 8, Tomaševski was approved as the first candidate of the list of the Electoral Action of Poles in Lithuania and the Union of Christian Families for the general elections scheduled for October 9.
Lithuania's parliament has recently amended electoral laws to the effect that MEPs and municipal council members would automatically lose their seats if they run in national general elections.
Tomaševski's decision 'makes things difficult for his party'
By not running for national parliament, Tomaševski will make it difficult for his party to compete in October's general elections, a political analyst said on Wednesday.
"I think his decision not to run means, in one or another way, that things will be very difficult for the Electoral Action of Poles in the upcoming elections," Mažvydas Jastramskis of the Institute of International Relations and Political Science at Vilnius University told BNS.
It is possible that Tomaševski decided not to run for a seat in the Seimas because he does not want to give up his MEP mandate, he said.
"I believe that the change in the regulation that requires that MEPs give up their mandate to run for the Seimas could have had an impact. The position and salary at the European Parliament is incomparable to that in the Lithuanian Seimas," Jastramskis said.
On the other hand, it is possible that Tomaševski is confident that the party is strong enough to win seats in the Seimas without its leader, the analyst said.
It is also possible that the MEP has received criticism from Polish politicians, he added.