Stephen Gilbert MP said he "feared at worst" that the woman he helped rescue from the Thames was dead.
He said: "I feared at the worst it would be a body, I alerted the police, and they were called in to get a response, and then she moved, and I was able to chase down the terrace and grab one of the life-buoys, throw it in, made a reasonably good shot and she grabbed it."
He added, "I guess it's just the right time, right place and I was delighted to help.
The Metropolitan Police had said they pulled a woman from the water after MP Stephen Gilbert claimed he rescued her:
"At 1950 the marine policing unit responded to reports of a woman in the River Thames near Westminster Bridge. They recovered her from the water and took her to hospital. Next of kin have been informed," the force said in a statement.