"It is a well-known fact that the terrorist organisations, backed by the ISI, are actively involved in almost all terrorist activities carried out in the country," BJP President Rajnath Singh said.
The existence of more than 5,000 sleeper modules operated by ISI is a clear indication that India is virtually sitting on a tinder box, he added.
He alleged that the ISI-sponsored terrorism was thriving in the country due to the UPA government's failure to take stringent action to curb terrorism succumbing to "vote bank politics".
The series of blasts in different parts of the country, including the serial explosions in Jaipur on Tuesday, were the handiwork of ISI-backed terrorist organisations, Singh alleged.
Disagreeing with the argument that Jaipur blasts reflected intelligence failure in BJP-ruled Rajasthan, he said, "Terrorism is not a law and order problem but a national issue. We need a stringent central act on the lines of POTA to deal with terrorist activities".