Neil Findlay said her decision to head to Australia to take part in the reality TV show demeans politics.
Her successor as Scottish Labour leader, Richard Leonard, has confirmed the party’s MSPs are to consider whether to suspend her for going to the jungle.
However, Labour leader Jeremy Corbyn has said she should not be suspended and that it is her choice.
Mr Findlay, a regional MSP for Lothian, said politicians should be working for their constituents, not jetting off to the jungle
He told BBC One’s Sunday Politics: “I think it’s utterly ludicrous, a ludicrous position.
“We have a situation where we’re in the run up to the budget in Scotland, where local government is on its knees, where the NHS is showing pressures like never before, when people’s living standards are falling and they expect their MPs MSPs, councillors, elected representatives to be in fighting on their behalf and I don’t think people would expect them to jet off around the world and sit around the camp fire eating a kangaroo’s appendage.
“I think it demeans politics when people get involved in that.
“We’ve got a pretty serious job to do, people out there are struggling and there’s huge pressures on public services and that’s the job we should be doing.
“I take my job very seriously and so do my colleagues and I think they would expect better.”
Ms Dugdale will join the likes of boxer Amir Khan, Boris Johnson’s father Stanley and The Saturdays singer Vanessa White in the jungle for the ITV show which starts on Sunday.
News of her participation in the programme drew criticism and reactions of surprise from other politicians.
Economy Secretary Keith Brown MSP (SNP) told Sunday Politics: “The fundamental point in this is the commitment of parliamentarians to their primary job which is to represent people and I think that’s very important.”
He said the question of suspension was a matter for the Labour Party, not the Scottish Parliament.
Mr Brown said: “She will not be breaching, as I understand it, any of the rules in the Scottish Parliament but it’s a question of how her party views her absence from her primary job, the day job, of being an MSP.”
Ms Dugdale became the leader of Scottish Labour after the party’s trouncing in the 2015 general election, in which it lost 40 of the 41 seats it had held north of the border to the SNP.
She stepped down suddenly in August, prompting the leadership contest, with both Mr Leonard and fellow MSP Anas Sarwar vying to succeed her.
Speaking in Glasgow just after he was elected leader on Saturday, Mr Leonard said he was “a bit disappointed” by Ms Dugdale’s decision.
He said suspension was not his initial reaction but added: ‘’I think it’s something the group will have to consider.’’
But Mr Corbyn told the Press Association: ‘’It’s her choice to go on I’m A Celebrity...Get Me Out Of Here!, I don’t think it’s appropriate to suspend someone from the party for doing that, that’s her choice.’’