Vajpayee, who heads the Hindu nationalist BJP party, said on Friday at the funeral of Ramchandra Paramhans that he would fulfil the 93-year-old priest's dying wish to build a temple in the northern city of Ayodhya at the reputed birthplace of the god Ram, where a mosque was built in the 16th century.
In 1992 Hindu zealots led by Vajpayee's then-opposition BJP tore down the Babri mosque, setting off nationwide riots that left more than 2,000 dead. The dispute over the site is now before the courts.
Congress party spokesman S. Jaipal Reddy called Vajpayee a "powermongering opportunist."
He noted that Vajpayee had earlier made statements calling for a peaceful settlement to the Ayodhya dispute either through the courts or negotiations.
Babri mosque pre-1992, when it was destroyed by Hindu zealots
"Vajpayee likes to have his cake and eat it too. When he sees his position in the party getting weakened, he comes out with such statements," Reddy told Agence France Presse.
"The prime minister keeps making flip-flops all the time on vital issues ... we don't know which is true," Reddy said.
"It is a very calculated statement by a crafty politician trying to perform a balancing act."
Vajpayee, addressing hundreds of mourners for Paramhans just a few kilometres from the mosque's rubble, said Friday: "Nothing is impossible."
"Everyone should try to fulfil his (Paramhans') dream. I shall fulfil his last wish," Vajpayee said.