The 69-year-old Gordon MP, who is due to step down from the Commons at next year's General Election, beat the challenge from the Solihull MP by just three votes. He said his 30-year experience at Westminster helped swing the vote his way.
But Gloria De Piero, Labour's Shadow Minister for Women and Equalities, was critical.
"This result comes as little surprise when you remember Nick Clegg leads a parliamentary party which has as many men with knighthoods as it has women MPs."
She added: "When it comes to women's representation, the Lib Dems really need to move up a gear. With just seven out of 57 MPs, they score even worse than the Tories."
After his election, Sir Malcolm said the Lord Rennard row would be dealt with "swiftly and privately".