Ms Dugdale, a Lothian MSP and current Labour deputy leader, is favourite to take the helm following the resignation of Jim Murphy in the wake of the party’s general election disaster in Scotland.
Ms Lamont said Labour was still in shock and warned there were no quick fixes. But she said Ms Dugdale was bright, brave and compassionate.
Writing on the website Labour Hame, Ms Lamont said the job had to be a “long-term, long-haul appointment”.
She continued: “Too often our party comes together to elect a leader and then steps back, arms folded, waiting to be disappointed.
“We cannot allow that luxury now. Choosing a leader must be for the long term. There is no quick fix, no gimmick, no short-term ploy that will match the respect we need to show those who have turned away.”
Ms Lamont, who backed former Labour MP Katy Clark in the deputy contest last year over eventual winner Ms Dugdale, said she now believes the MSP is the “woman to lead the change” in Labour.
She praised Ms Dugdale’s campaign against payday loans, saying: “She is bright, talented, compassionate. She is brave. She is wise enough to have taken time to decide whether she wants the job.
“Her instinct is to co-operate and that is good. 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.”
Meanwhile, Mr Macintosh launched his leadership bid, arguing Scottish Labour needs to stop defining itself by opposition to the SNP and Tories.
He said: “The Scottish Labour Party is a great movement – we represent a broad church of ideas, a vehicle for common good and a champion of progressive change and equality for all, but we have lost the trust and the faith of the people of Scotland.
“Our fightback will not be successful unless we stop defining ourselves and our party by our opponents. We need to take a fundamentally different approach to our politics.
“I do not want to ask people to vote Labour to block the Tories in London or to stop the SNP in Edinburgh – I want them to want to vote Labour because we have the ideas, the vision and the values to deliver a better future for Scotland.” He said devolution offered a new way of doing politics in Scotland, which was less tribal and confrontational and more collaborative.
“That is why I am standing to be leader of Scotland’s Labour Party. It is time we focus on Scotland’s future, not Labour’s past,” he said.