Jeremy Corbyn's spokesman hit out at Barack Obama in the early hours of Tuesday morning after the US President appeared to criticise the direction the Labour leader was taking the British left.
In an interview for CNN, Obama had told political pundit David Axelrod that he believed he could have beaten Donald Trump in November if the US constitution had permitted him to run for a third term.
Asked whether he was worried Hillary Clinton's would see the Democratic Party pivot to the left - as in the UK under Jeremy Corbyn - he said that even Bernie Sanders was a centrist compared to the current Labour leader.
"I don't worry about that partly because I think that the Democratic party has stayed pretty grounded in fact and reality," he said.
"[The Republican party] started filling up with all kinds of conspiracy-theorising that became kind of common wisdom or conventional wisdom within the Republican party base. That hasn't happened in the Democratic party. I think people like the passion that Bernie brought, but Bernie Sanders is a pretty centrist politician relative to ... Corbyn or relative to some of the Republicans," he added.
But in a statement to the Guardian hours after the comments were revealed on Monday night, an aide for the Labour leader argued that both Labour and the Democrats would have to work on changing a system that did not deliver for the majority of people in the US and the UK.
"What Jeremy Corbyn stands for is what most people want: to take on the tax cheats, create a fairer economy, fund a fully public NHS, build more homes, and stop backing illegal wars," he said.
"For the establishment, those ideas are dangerous. For most people in Britain, they're common sense and grounded in reality."
Despite ostensibly coming from similar sides of the political divide, Corbyn and Obama - who have only ever met for around 90 minutes - have very little in common. Corbyn is anti-intervention in Iraq and Syria while Obama has spearheaded US backing for so-called moderate Syrian rebels and the Iraqi army fighting Islamic State (Isis) in Mosul.
Likewise, Corbyn is sceptical of free trade deals that are seen to prioritise corporate interests above national sovereignty, such as Obama's Trans-Atlantic Trade and Investment Partnership (TTIP).
Corbyn was not the only person to hit back at Obama in the closing hours of the festive period over the CNN interview. Donald Trump - never one to miss a middle-of-the-night Twitter tirade - reacted angrily to Obama's claim that he could have beaten him in November.