"It is understandable that legislators are looking for adequate legal protection for other forms of cohabitation. However, this cannot be done by changing the concepts of family or marriage," the Lithuanian Bishops' Conference said in a letter.
"Equating various other forms of cohabitation with the family by ignoring the natural complementarity of the sexes, inevitably negates the natural nature of the family and erases it as the constitutional basis of society and the state," they said.
The letter was published a few days before the new center-right government is expected to take office.
In their coalition agreement, the conservative Homeland Union–Lithuanian Christian Democrats, the Liberal Movement and the Freedom Party agreed to strive for "recognizing in law the gender-neutral partnership".