Speaking a day after Washington accused Russia of supplying attack helicopters to Assad's forces, Alexei Pushkov said Western calls for the Syrian president to step aside were "irresponsible".

"The West does not have any policy at all towards Syria. You are lucky to have Russia, because by blaming Russia you have the possibility to say that somebody is preventing you from solving this crisis," Pushkov, chairman of the State Duma Committee on Foreign Affairs, told reporters at a news conference London.

"What I hear from the West is absolutely irresponsible. Look at what (U.S. Secretary of State) Hillary Clinton says. She says Assad must go. What, is this a policy? What happens next?", Pushkov added, citing the threat of Iraq-style civil war.

Along with China, Russia has repeatedly blocked tougher sanctions against Assad at the United Nations, arguing such action is not the answer to the government's bloody crackdown on its opponents.

Although Moscow remains a key arms supplier to Damascus, it has denied sending Syria weapons that could be used in the conflict, while Syria's ambassador to Moscow has said Russia is not sending Damascus attack helicopters.

SCEPTICISM

The United Nations says more than 10,000 people have been killed by government forces, while Syria says at least 2,600 members of the military and security forces have been killed by what it calls foreign-backed "Islamist terrorists".

Pushkov said the conflict in Syria should be "viewed through the lens of Iraq and Libya", adding that Western intervention in Iraq was a "massive fraud" for which no one has been held accountable.

He also cast doubt on the motives of Sunni Muslim Saudi Arabia and Qatar, two of the strongest advocates for Assad's removal, saying the argument that the two non-democratic states would help bring democracy to Syria "does not hold water."

World powers are working towards holding a crisis meeting on Syria in Geneva on June 30 to try to revive a battered U.N. and Arab League peace plan for the cessation of violence and negotiations between Assad and his opponents.

France has also called for humanitarian corridors to be set up within Syria.

But Pushkov dismissed that idea, saying such corridors could be used by anti-Assad rebels for shelter.

One option Russia is considering is a transition of power similar to that seen in Yemen last year, when former President Ali Abdullah Saleh was granted immunity from prosecution for the killing of protesters as part of a power transfer deal.

Otherwise Pushkov said the options were limited.

"I don't think we have clear answer. If you ask me, do you have a plan on the table? I would say no we don't, but nobody has."

(Reporting by Mohammed Abbas; Editing by Andrew Osborn)