The Labour leader has been targeted by some opponents of leaving the EU who believe his acceptance of Brexit stands in the way of the party signing up to a new public vote – a potentially decisive shift.
The clash will come to a head at Labour’s annual conference next month, when up to 200 local party branches will attempt to make a further referendum official party policy.
Now a leaked memo from the People’s Vote has told supporters: “This campaign is not about Jeremy Corbyn and we must not – will not – use it to damage or undermine the party’s leadership or attack them personally.”
Penned by the group’s head of communications, Tom Baldwin, it comes amid growing confidence that there will be a showdown at Labour’s conference in Liverpool.
The ruling body of the grassroots pro-Corbyn group Momentum will meet on Saturday to decide whether to canvas opinion, after more than 4,000 members signed a petition calling for a conference vote.
The pressure illustrates a growing clamour from Labour members within Mr Corbyn’s base on the left of the party, as well as among many mainstream MPs.
Pro-referendum motions are being considered by more than 200 constituency Labour parties and have already been passed for submission to conference by at least 13, Momentum says.
Labour hopes to force Theresa May into another general election if her Brexit deal is rejected by parliament this winter, or if she fails to strike any agreement at all.
However, the party has been edging closer to backing a referendum, with both John McDonnell, the shadow chancellor, and Keir Starmer, the shadow Brexit secretary, insisting it must remain an option.
Significantly, polling has found strong support among Labour’s target voters with 59 per cent of non-supporters who “might” or “would seriously consider” getting behind the party favouring a fresh referendum.
Mr Baldwin’s memo, seen by the BBC, stresses that the tone of the People’s Vote campaign will be crucial to its success in winning Labour backing.
It emphasises that “whatever views supporters have about the overall direction of the Labour Party, the campaign should not be used to attack Jeremy Corbyn personally”.
More than 712,000 people have signed our Final Say petition to give the final decision on any Brexit deal to the British people, while around 215,000 are backing the very-similar People’s Vote campaign.
However, the push was strongly criticised today by Andy Burnham, Labour’s mayor of Greater Manchester, who argued it would “deepen that rift” in the country.
“My frustration with those leaping to a second referendum is it further inflames this idea of an arrogant political class which isn’t listening, and isn’t dealing with the issues that gave rise to the referendum in the first place,” Mr Burnham told the Politico website.
The Independent has launched its #FinalSay campaign to demand that voters are given a voice on the final Brexit deal.