David Blunkett called for the Labour Party to change the way it deals with disputes, as news of Jared O'Mara's decision broke last night.
Speaking exclusively to The Star, Lord Blunkett, who represented the Sheffield Brightside and Hillsborough constituency for 28 years, said everyone was welcome in the party but lessons must be learnt.
He said: "I'm extremely saddened and hurt for the sake of the people of Sheffield Hallam, for Labour Party members who have worked so hard and given so much support to Jared himself whose personal experience has clearly been so damaging that it has led to this decision.
"It is critical that whatever the circumstances, the personal accusations and untruth which Jared has experienced end.
"The people of Sheffield Hallam should be properly represented and to that end, political differences should be set aside in the interests of our city.
"I personally wish to make it clear that those, like myself, from working class backgrounds, who have experienced struggles in their early years and have the privilege to represent and fight for people we care about, have been and always will be welcome in the Labour Party.
"There is is one further lesson which I hope my party nationally will learn. We cannot and must not leave people under a cloud for almost 12 months rather than having a clean, speedy, fair dispute system. How we treat individuals is how we treat the nation."