The Downing Street aide at the centre of the cash-for-peerages inquiry has been left isolated with nobody to confide in, her mother said yesterday.

Marie Turner said that Ruth Turner had been through a harrowing ordeal since her arrest, adding that she was innocent in the face of mounting allegations.

Her intervention comes as the inquiry centres on Ms Turner, one of Tony Blair’s closest allies, and her meetings with Lord Levy, Mr Blair’s personal fundraiser. It has been claimed that their relationship is at the centre of an alleged cover-up.

Mrs Turner, speaking from the home she shares with her husband in America, said that her daughter, Downing Street’s head of government relations, was under enormous stress.

“It is unimaginable to think what she must be going through. She has nobody to talk to at all. As far as we know this must be one of the stresses for her,” she said.

Mrs Turner, who lives in Connecticut, told a newspaper: “We are at a great distance and she cannot talk to either of us — that leaves her to carry a heavy stress on her shoulders alone.”

“I presume that you are never more alone than when you are sitting in a police station.”

She added: “Doesn’t any mother think her daughter is incapable of criminal activity?”

Mrs Turner, who moved from Cambridge when her husband Denys got a job at Yale University, added: “There just seems to be leaks and more leaks. I don’t know who leaks, but I wish that it wasn’t happening. It is enormously stressful, of course. She is above board, honest, and her integrity is beyond reproach.”

She said that Ms Turner, 36, who is unmarried, has resolutely refused to discuss her job. “I have made it a principle not to discuss the job with her in any form which means what I don’t know, I can’t say.

“Frankly since this blew up I was unaware of what she was doing. I have discovered more now than I never knew before.”

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