New Delhi, Oct 11 (IANS): Casting doubts on the credibility of Anna Hazare over his links with the Rashtriya Swayamsevak Sangh (RSS), Congress leader Digvijay Singh Tuesday asked the activist why he was opposing the Congress when parliament had supported his demands on the Lokpal bill.

Digvijay Singh said in an open letter to the activist: "Your statements that you are not aware of RSS supporting your cause, raise doubts about your credibility."

"Whenever I have mentioned involvement of RSS with your anti-corruption movement, you have suggested I be sent to a lunatic asylum," he said.

Questioning Hazare's recent statements asking people to vote against the Congress in the Hisar by-poll in Haryana, Digvijay Singh said: "If you are seen along with the corrupt in your fight against graft, how will the menace be curbed."

The Congress general secretary asked Hazare to trust parliament, which endorsed his three demands on the anti-corruption Lokpal bill, and wondered why he had still asked people to vote against Congress.

Digvijay Singh said it was good that clean people like Hazare joined mainstream politics.

"You must think who is benefiting from your decisions. When you oppose the Congress, who are you seen with," Digvijay Singh asked.