Video grab shows Senate Intelligence Committee Chairwoman Feinstein speaking on the floor of the U.S. Senate in Washington Thomson Reuters

LONDON (Reuters) - A powerful British parliamentary committee will ask the United States to hand over blacked out parts of a report into the CIA, to try to establish whether British spies were complicit in torture or rendition, its chairman said on Sunday.

If parliament's Intelligence and Security Committee (ISC) saw evidence of such behavior, it could summon politicians from the left-leaning Labour party such as former prime minister Tony Blair who were in power at the time of the allegations.

"If British intelligence officials were present when people were being tortured then they were complicit in that torture," Sir Malcolm Rifkind, the ISC's chair and a former foreign secretary, said.

"That would be quite against all the standards of this country. It would be something that ought to be brought into the public domain," Rifkind told the BBC's Andrew Marr Show.

A report by the U.S. Senate Intelligence Committee released last week found that the CIA had misled the White House and the public about its torture of detainees after the Sept. 11 attacks and had acted more brutally than thought.

Its publication has already raised uncomfortable questions in Poland and other countries identified as being involved in the program about how much their leaders knew.

The British government said it had asked the United States, a close ally, to keep parts of the report referring to UK intelligence activity secret on national security grounds. It insisted it was not covering up anything embarrassing.

Britain's foreign and domestic security services, known as MI6 and MI5, have for years been accused of colluding in the ill-treatment of suspected militants.

But the heads of MI5 and MI6 have repeatedly said they would never use torture to gain information, and ministers have also denied knowledge of sending suspects to face torture abroad.

However, a Libyan dissident asserts he and his pregnant wife were kidnapped by U.S. forces in 2004 with the help of MI6 and handed over to Muammar Gaddafi’s government, which tortured him.

A Pakistani man also says he was waterboarded by British special forces in Iraq in 2004, and a former Labour security minister says there may have been "the odd case" when British spies knew of U.S. torture.

Rifkind said his committee would be asking both the U.S. Senate and the U.S. government to give it access to the relevant parts of the report into the CIA as part of its own inquiry into the work of Britain's intelligence services.

If necessary, he said the committee would summon spies and current and former ministers to learn the truth. He said he hoped his committee's report into the matter would be ready next year.

(Editing by Philippa Fletcher)