Talking to reporters outside the Reliance Energy office in Kandivali where he is on a hunger strike, Nirupam said he would immolate himself outside Reliance ADA group chief Anil Ambani's house, if his demand was not met.
Nirupam wants Maharashtra Chief Minister Prithviraj Chavan to announce audit of all power companies supplying electricity to Mumbai.
He said his fast has entered the third day and his health was good.
"Sugar levels are fluctuating but I will continue with my hunger strike," the MP from Mumbai North said, adding that he would continue his agitation till the demand was met.
Mumbai suburbs guardian minister Mohammed Arif Naseem Khan, city Congress president Janardhan Chandurkar and senior leader Kripashankar Singh visited Nirupam at the fast site and offered their support.
Mumbai was excluded from the recent government's decision of 20 per cent cut in power tariff charged to domestic consumers, industries and powerlooms by the state-run Maharashtra State Electricity Distribution Company (MahaVitaran).
The state Cabinet had last week decided that the concession of 20 per cent power tariff cut would be applicable to consumers with consumption of less than 300 units.
The reduction in power tariff will not be applicable in the metropolis where players are other than MahaVitaran supply power. Mumbai consumers get power supply from Tata Power, Reliance Infrastructure and Brihanmumbai Electric Supply and Transport undertaking.