Sen, who had been elected to West Bengal assembly four times from Jalpaiguri constituency until 1991 on Congress ticket, was ailing for some time due to geriatric problem, his family said.
The 89-year old, who had been admitted to a local private hospital five days back, haad switched over to TMC from Congress in 1998.
A practising physician he was popular among the poor in Jalpaiguri town for treating them free of cost, several local leaders said while condoling his demise.
Sen left behind one son and two daughters.