Tony Blair has claimed Labour faces "annihilation" at the next general election and could fail to be in government again if Jeremy Corbyn becomes leader.
The former prime minister warned the party is in “danger more mortal” today than at any point in its existence as veteran left-winger Mr Corbyn continues to remain the frontrunner in the contest.
Mr Blair directed his remarks at long-standing members and called on them to “save the party” and heed his warnings, regardless of whether they used to “support me or hate me”.
Writing for the Guardian, Mr Blair said voters would punish the party as they would view themselves as “victims” of the Conservative-led government’s policies and Labour’s self-indulgence.
He said: “The party is walking eyes shut, arms outstretched, over the cliff’s edge to the jagged rocks below.
‘Moment for a rugby tackle’
“This is not a moment to refrain from disturbing the serenity of the walk on the basis it causes ‘disunity’. It is a moment for a rugby tackle, if that were possible.”
He made his latest intervention after previously warning Labour had “rediscovered losing” as a poll predicted Mr Corbyn was ahead in the contest.
In new comments, Mr Blair said the election to replace Ed Miliband as leader is now about whether Labour "remains a party of government", as he noted protest movements agitate against those who govern rather than change the country.
Supporters of Mr Corbyn have the numbers to “mount a partial takeover” and do not think it matters if Labour wins an election, while “some actually disdain government”, Mr Blair said.
He also claimed a “throwback” to the 1980s was taking place without the stability and sense offered by the unions of that time, along with left-wing politicians who had experience of government and constituencies which would always back Labour.
Mr Blair said: “If Jeremy Corbyn becomes leader, it won’t be a defeat like 1983 or 2015 at the next election.
“It will mean rout, possibly annihilation. If he wins the leadership, the public will at first be amused, bemused and even intrigued.
“But as the years roll on, as Tory policies bite and the need for an effective opposition mounts - and oppositions are only effective if they stand a hope of winning - the public mood will turn to anger.
‘Our self-indulgence’
“They will seek to punish us. They will see themselves as victims not only of the Tory government but of our self-indulgence.”
Mr Blair added the ongoing policy debate within the party has already done “immense damage” and largely failed to relate to the challenges of the modern world.
He went on: “There is a vast array of policy questions to answer. We’re not even asking them right now. We know where this ends. We have been here before.
“But this sequel will be a lot scarier than the original. So write it if you want to. Go over the edge if you want. But think about those we most care about and how to help them before you do.”