Barun Makhan, a ruling TMC member, was arrested from the Gadiala area, said police.
Seven others were earlier arrested in the case who were sent to 7 days of police custody.
The two victims, one in her mid twenties and her mother-in law were in their home on Tuesday night when eight persons barged in and raped them before escaping, police said.
The CPI (M) and Congress have alleged that TMC supporters were involved in the gang rape and the ruling party was trying to shield them.