The Green Party of England and Wales this weekend enacted what they describe as clause IV moment in reverse, as delegates at its 40th Spring Conference in Nottingham voted for a left-turn in the constitution.

The statement of core values, which previously focused only on environmental principles, was amended to include a commitment to social justice and a transformation of society for the benefit of the many not the few, on the day that the party celebrated being 40-years old.

A substantial majority 71% of conference delegates voted in support of the change, which condemns the dominant economic system based on inequality and exploitation and calls for a world based on cooperation and democracy.

Student member Josiah Mortimer proposed the motion, saying in his speech The past few years have shown that the Greens are the real party of social justice this motion is therefore fundamental in enshrining that shift into the partys core.

He added: At a time when Labour are failing to stand up to the coalitions austerity policies, it is essential the Greens make our position clear that we are on the side of ordinary people and the planet.

Party leader Natalie Bennett said: The Green Party has for many years been the chief champion of social justice in British politics. Our elected representatives and campaigners have led the way in living wage campaigns, in protecting essential public services and speaking up for benefit recipients, asylum-seekers and refugees and the disabled, in the face of demonisation. This change reflects the existing nature of the party.

At the same conference, Bennett called for an end to poverty wages, child poverty and pensioners being unable to heat their homes in her keynote speech.