Maria Eagle could also be switched with Labour leader understood to want his top team to speak with one voice on foreign and defence issues

Jeremy Corbyn is ready to offer the shadow foreign secretary, Hilary Benn, a move to another shadow cabinet post in what is likely to be an imminent, high-risk reshuffle aimed at ensuring that his top team speaks with one voice on foreign and defence matters, the Observer understands.

The Labour leader may make a series of highly controversial changes within days that could also include a switch for defence spokeswoman Maria Eagle.

The reshuffle – while not finalised, and with no date yet set – is being planned principally as a way to avoid the Labour leader publicly voicing opposing views to members of his shadow team on their specific briefs.

Corbyn believes that the party is remarkably united on most domestic issues, including economic policy, and that it now has to present a similar front on foreign affairs and defence in votes on key issues such as Trident in the coming months.

But if Benn and Eagle are singled out, it will be seen by detractors in the parliamentary Labour party and shadow cabinet as a declaration of war, particularly as Corbyn began his leadership promising to allow everyone on the front bench the freedom to express differing views. Among those who, colleagues say, could quit the shadow cabinet in protest are Angela Eagle, who is Maria’s sister and chair of the National Policy Forum. Benn and Eagle may refuse other posts.

Several Labour backbenchers, writing in today’s Observer, suggest Corbyn should avoid a damaging and divisive reshuffle and concentrate instead on attacking the Tories over issues such as cuts to funding on flood defences and Europe. One shadow cabinet member predicted that Corbyn would pull back and avoid removing Benn as shadow foreign secretary. “He would be mad to do it. These things are much easier to talk about than to do. There could well be a walkout.”

Tensions are likely to be stoked further by news that John McDonnell, the shadow chancellor and Corbyn’s right-hand man, has invited self-declared Marxist and leading anti-EU voice Yanis Varoufakis, the outspoken former finance minister of Greece’s leftwing Syriza party, to speak at one of the first of a series of public meetings on the “new economics”, which he is staging to help frame a fresh party approach to economic policy.

Varoufakis has accepted the offer, though no date has been finalised. Last year Varoufakis wrote that “Karl Marx was responsible for framing my perspective of the world we live in, from my childhood to this day”.

When are Labour party ‘moderates’ going to do more than just moan? | John Harris Read more

Pat McFadden, Labour’s Europe spokesman, said that, while it was good to have an open debate, he hoped that Labour’s official sister parties in the EU, such as those in power in France, Germany and Italy, were not being overlooked. Other Labour MPs fear the invitation shows the true anti-EU feelings of Corbyn and McDonnell. The events will be open to the public and will feature members of Labour’s economic advisory council, which includes Nobel prize winner Joseph Stiglitz and other leading economists such as Thomas Piketty and Mariana Mazzucato.

In a recent free vote on airstrikes on Islamic State targets in Syria, Benn made a widely acclaimed speech in the Commons backing airstrikes after Corbyn had spoken out against them. Eagle, meanwhile, supports renewing the Trident nuclear missile system, as stated in Labour’s general election manifesto, while Corbyn opposes Trident. Many senior Labour figures say the party will erupt into civil war if leftwinger Diane Abbott is promoted from international development to either foreign affairs or defence.

The more likely scenario is that Benn could be replaced by Emily Thornberry, the former shadow attorney general who quit Ed Miliband’s shadow cabinet following a row after tweeting a picture of a house with a flag of St George and a white van while campaigning against Ukip in Rochester.

Stephen Kinnock, writing on Labour’s prospects for 2016, said: “A reshuffle would simply leave people confused about what this fabled ‘new kind of politics’ is all about. It’s a waste of time and energy”. Fellow backbencher Wes Streeting said: “Over Christmas, we should have been taking the Tories to task over their budget cuts for flood defences. Instead, damaging briefing from the top of the party meant Labour’s main message was about a shadow cabinet reshuffle.

“This is no time for divisive reshuffles or an introspective debate about party structures.”

Neil Coyle, another first-term Labour MP, said: “The idea that Corbyn must only include clones and drones in the shadow cabinet is farcical.”