Richard Burgon has said he will give Labour members the final say on if the party back military action if he is elected deputy leader.
The Shadow Justice Secretary has said he plans to change Labour's constitution to give members a veto on military action supported by the leadership.
While there would be an exception for cases of national emergency or when there is UN backing, it represents a bold attempt to move foreign policy decision making beyond MPs.
In a speech in Oxford, Mr Burgon said the party could have avoided the "disastrous and illegal" Iraq War if it had listened to members
He will say: " Labour remains scarred by the experience of the Iraq War – for many it is sadly the single act for which the last Labour government is most remembered.
"It was a conflict opposed by most Labour Party members at the time.
" Jeremy Corbyn rightly apologised for Labour’s role in the disastrous and illegal war at the time of the publication of the Chilcot Report in 2016.
"But even since Iraq, Labour mistakenly backed the intervention in Libya, which has had catastrophic consequences for that country, and contributed to a massive refugee crisis.
"These interventions were supposed to have made us safer from terrorism. Tragically, they have failed in that objective too."
Mr Burgon will demand that Labour supports foreign policy that is "robustly independent" of the United States and argue for the "explicit backing" of party members for any military intervention.
He will add: "With this pledge in place, the British people can be confident that the Labour Party will not repeat the mistakes of the past and wrongly back military conflict.”