K U Arunan, the party's Irinjalakuda MLA, had inaugurated a book distribution function, organised as part of the first death anniversary of RSS leader P H Shine at Irinjalakuda on Monday.
As the controversy erupted, Arunan, a former college professor, said he was unaware that the function was organised by the Rashtriya Swayamsevak Sangh.
CPI(M) Thrissur district secretary K Radhakrishnan told reporters here that the party has publicly censured the MLA for attending the RSS function.