"The move of the 'pro-Taiwan' members of Seimas poses a gross interference in China's domestic affairs, and a severe violation of the basic norms governing international relations as well as the UN Charter," the embassy said in a statement.
"The Chinese government appreciate the Lithuanian government's long-term commitment to one-China policy and the Seimas' great contribution in promoting bilateral relations. We believe that the letter of some members of Seimas does not represent the official position of Lithuanian government and the Seimas’ general attitude towards its friendly cooperation with China."
The embassy said that the move "runs counter to the consistent position of the Lithuanian government and its pledge of no official contact with Taiwan region, thus damaging the international image of Lithuania".
"We hope that members of Seimas, as representatives of public opinion and participants in global affairs, respect the truth and international norms, show their respect to the sovereignty and territorial integrity of China, as China always does to the independence and sovereignty of Lithuania, and play a positive and constructive role in the sound development of China-Lithuania relations," it said.
Eighty members of the 141-seat Seimas from across the political spectrum, including Health Minister Aurelijus Veryga, have signed a letter to the WHO director general, calling for Taiwan to be granted access to the annual World Health Assembly (WHA) in May.
Taiwan's status is one of the most sensitive issues for China. Beijing sees Taiwan as part of China awaiting unification and has sought to reduce the island's presence in international organizations.
Like many other countries around the world, Lithuania does not recognize Taiwan's independence and supports the "one China" policy.
In their letter, the members of the Seimas underline that Taiwan is located "at a strategic node in the Indo-Pacific" region and is in "high need for disease prevention, as people and goods are constantly entering and leaving" the island.
The letter was initiated by MPs Mantas Adomenas and Gintaras Steponavicius.