Ashok Bairagi was shot in the Basirhat railway station premises in North 24 Parganas district on Thursday.
Utpal Naskar, Superintendent of Railway Police, Sealdah, said Bairagi was shot in his back twice by the attacker, who managed to escape.
State Minister Jyotipriya Mallick, who is also the district TMC chief, said Bairagi has been admitted to RG Kar Medical College and Hospital in Kolkata where doctors have said his condition was critical.
Blaming BJP for the shooting, he said the incident was a result of BJP's conspiracy and alleged that the party was bringing in weapons from Bangladesh with the help of BSF.
BJP MLA from Basirhat South Samik Bhattacharya, when contacted, said the incident was a result of intra-party rivalry.
"There is no necessity to comment on the charges levelled against BJP (by Mallick). The general people will surely understand this (incident)," he added.
[With agency inputs]