Having previously described the battle between current leader Jeremy Corbyn and prospective Smith as Labour's "summer of discontent" he acknowledged the need for more unity in the party following a post-Brexit Britain.
McLeish, who has been a Labour party member for over 40 years told Sputnik about his concerns for the current state of the Labour party.
"This phase is not only a fight for the leadership of the party, but it is a new way forward for Labour during a time when the Tory party is running amock, because we just have no effective opposition."
When asked about the possibility of a future split in the party with regard to the differing brands Owen and Corbyn bring to the upcoming leadership, McLeish said:
"The Labour party will continue to be a serious force in parliament in representing the concerns of the working people, but I feel that under a leadership of Jeremy Corbyn there are far too many aspects of support missing for him."
He went on to add:
"The consequences for any such split within the party would not only be tragic for the party but also dire for Britain as a whole. I believe as many do, that to win an election you must have both parliamentary people and party working in unison.
"Based on Corbyn's politics, in my opinion we would see Labour leading itself into the wilderness for a very long time!" McLeish told Sputnik.
Mr. Corbyn who is the odds-on favorite to win the leadership contest due to conclude in September is "not the answer to Labour's decline or long-term recovery," Mr McLeish insisted.
He has also been very outspoken about what he feels is a need for Scottish Labour to start thinking beyond the upcoming leadership battle.
Henry McLeish backing Owen Smith in #LabourLeadership https://t.co/jz6BEsfXbz
— Jack Foster (@jackfostr) August 22, 2016
He told reporters last month that the party must even go as far as considering to sever ties with the UK, claiming: "Jeremy Corbyn wrecks its chances of winning the next General Election."
Mcleish has also described what he predicts as a future of home rule for Scotland and a form of federalism, independence or some other, as yet unknown, four-nation constitutional solution.
