Scottish Labour needs to stop defining itself by its opposition to the SNP and the Tories, Ken Macintosh said as he formally launched his leadership campaign.
The Eastwood MSP, who also stood to be party leader in 2011, will compete with Kezia Dugdale for the job.
Jim Murphy is stepping down as party leader later this month after Scottish Labour lost all but one of its MPs north of the border to the SNP. He survived a motion of no confidence but announced he will step down after tabling a report on how the party should move forward.
Last month, Mr Macintosh said his supporters were being “bullied and intimidated by the party machine” in an attempt to close down a leadership contest but with enough official support he is now formally launching his campaign.
He has called for a major shake-up of the way the party elects its leaders and wants a move from the current electoral college system to one member one vote, and he also favours introducing open primaries, where leadership candidates could be questioned by registered supporters of the party rather than just paid-up members.
He said he will be a “reformist” leader and called on party members and affiliated organisations to support his proposals to change the rules of electing a new leader.
Mr Macintosh launched his candidacy after meeting students at Glasgow University today.
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.
“I have been in the Labour Party all my adult life, but I only stood for election because I believe in the Scottish Parliament. Devolution offers a new way of doing politics in Scotland, less tribal and confrontational, more collaborative, more about sharing power with civic Scotland, with the voluntary sector, with businesses, with the people of Scotland.
“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.”
Mr Macintosh set out his proposals for the leadership election in a letter to Mr Murphy, Scottish Labour Party chair Jamie Glackin and general secretary Brian Roy.
They include reducing party joining fees during the leadership contest, in a bid to attract more members, and holding the leadership contest quickly.
Mr Macintosh added: “This is a time of exceptional political engagement in Scotland with people more interested in the politics of our nation than they ever have been before. That is why I am so disappointed that Scottish Labour has not played as full a role as we could in leading this debate.
“That is why I have called for the people of Scotland to have their say on the next leader of Scotland’s Labour Party.
“I believe holding open primaries throughout Scotland will offer us a real opportunity to engage with a politically energised electorate, to listen to their concerns, their hopes and their aspirations and allow our movement to share our principles and our passion for Scotland free from the constraints of an election, and to demonstrate in deeds not words, that the days of protecting or preserving the influence of vested interests are over.”