Among the many challenges facing the Labour Leave campaign is their name. This handful of anti-European MPs, led by serial maverick Kate Hoey, no more reflects Labour's settled view on Europe than the rebels who tried to vote down same-sex marriage in 2012 reflect Labour's settled view on equality.
In fact, Labour is more united now on Europe than it has ever been - not just in parliament but at every level. Despite intense lobbying from the eurosceptic fringe, a positive EU motion was passed by the party's conference in September, with not a single speech or vote against it from either the grassroots or the trade unions. As a party, we speak with one voice: Britain is unambiguously better off as part of the European Union.
In this context, today's usual suspects advocating Brexit ought to amount to no more than a historical footnote. But experience suggests that any insurgent group has a shot at the big time if it's prepared to fight dirty, and if it has money to burn, and for Hoey and co, money is not a problem. The group insists that it's funded by party members, glossing over the fact that the key member in question is none other than millionaire John Mills of anti-EU pressure group Vote Leave - a group which is chaired by Matthew Elliot of the Taxpayers' Alliance, and whose other sources of funding are a Tory banker and a Ukip spread-betting tycoon. In short, the coffers are not likely to run dry any time soon.
The other key question, then, is how far Labour's outers are willing to go in order to make their case. Last year they tried to call themselves the 'official Labour Leave campaign', but that particular gambit was quashed in short order. I expect their next tactic as the referendum looms will be to demand equal representation with their party on any platform discussing Europe, as if they represented one half of a genuine split in opinion rather than a self-organised fringe group.
We know the characteristic approach of right-wing eurosceptics. First, blame 'Brussels' for whatever hot potato is currently being tossed around, then push your own agenda as a follow-up. Hence the absurdity of, for instance, Ukip's campaign over the festive season trying to blame the EU for flooding in the north of England. That strategy works well for the eurosceptic hard right; but one might hope that raising the spectre of 'Brussels' to deflect from the government's failings would ill befit those on the left who ought to have no vested interest in covering for the Tories.
So one might hope. A leaked draft of Labour Leave's latest missive crossed my desk recently, and it does not make for encouraging reading. There's the usual hotchpotch of bizarre inventions, like the suggestion that we will have to give up our seat on the UN security council - we won't - that British universities are clamouring to escape the EU - they aren't - or that Norway can pick and choose which EU rules to adopt - it can't.
Charitably setting these aside, the headline bogeyman is TTIP, a possible future trade deal with the US. Now, Labour MEPs were among the first to point out that some of the ideas mooted here are plainly unacceptable. But it's nonsense to suggest that the way to avoid this is to leave the EU.
Quite the opposite. We can win this battle precisely because we are fighting it at EU level, where many share our concerns, and where we gain clout by teaming up with our neighbours - together we're the world's biggest economy. How do Kate Hoey and her friends think we'd be better off if we walked away? Without the EU, the Tories would have signed us up to a bilateral deal - with all TTIP's worst features - before you can say 'converging regulatory standards'.
This is what really baffles me about so-called 'Labour Leave'. One of the defining characteristics of the political left throughout history has been our willingness to stand up and fight for our values. We've never shied away from political battlegrounds, be they local, national or global.
And what the outers somehow fail to recognise is that Europe is just another battleground. The decisions made there affect us profoundly, whether we're part of it or not.
As Labour, we fight such battles every day - and when we work with our allies, we can win them. That's why the EU single market has rules to protect consumers, workers and the environment, and to deal with multinational companies. We need to develop and improve these rules - not trigger a race to the bottom by breaking up the EU.
Even if every single assertion made by Labour Leave turned out to be true this could only inspire us to fight even harder. The suggestion that we on the left should give up and walk away from the political battleground of Europe is worse than absurd - it is a betrayal of what we stand for.
Richard Corbett is the Labour MEP for Yorkshire & Humber and deputy leader of Labour MEPs