Johann Lamont has given her backing to Kezia Dugdale in the contest to become the new Scottish Labour leader.
The former leader, who stepped down in October, said the Lothians MSP was "bright, talented and compassionate".
She also said Ms Dugdale was of the "post referendum generation" and able to give the party a modern voice.
Writing on the Labour Hame website, she said: "As our education spokesperson she revealed a creativity, harnessed to a focus on what worked, not just what sounded good.
"She is a campaigner, recognising the abilities of those who understand the problems facing too many in our communities and have already developed answers.
"Her campaign on taking on the scandal of pay day loan companies has, even in opposition, offered protection to those in debt.
"She is all of these things but critically she is part of the post referendum generation, shaped by that debate but not scarred by the arguments of the pre Scottish Parliament generation - hers is the generation charged with healing divisions and responding to a changed Scotland."
She said Ms Dugdale's instincts were to co-operate with others, adding: "Her politics are grounded in making a difference and tackling inequality and that means she can be a powerful voice for action over rhetoric.
"She can give Labour a strong voice, a modern voice in our new Scotland.
"And if she wins, it will not be for us to fold our arms and watch; it will be for all of us to roll our sleeves up and together take responsibility for past failings and for the challenge the future so clearly presents.
"And in my view Kez is the woman to lead that change."
The endorsement came as leadership rival Ken Macintosh launched his campaign with a visit to Glasgow University.
He said Labour must stop defining itself by its opposition to the Tories and SNP.
Scottish Labour leader Jim Murphy announced his intention to step down later this month in the wake of the party's crushing election defeat at the hands of the SNP.
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