Hilary Benn appeals for members to elect Andy Burnham in Labour leadership race

Benn rejected the idea of a plot to oust Jeremy Corbyn if the veteran left-winger wins the leadership

Hilary Benn says Labour will seek to amend the referendum Bill (EPA)

Hilary Benn, the son of the late Tony Benn, has appealed to Labour members to elect Andy Burnham as party leader rather than Jeremy Corbyn, who was a close ally of his father.

Writing in The Independent, the shadow Foreign Secretary said Labour has always been a “broad church with lots of different views.” In a sideswipe at Mr Corbyn and the Blairite candidate Liz Kendall, he added: “We must not let this contest become a false argument between holding on to our values and gaining power. Labour wins when we do both.”

On 29 July Mr Corbyn named Tony Benn as his favourite MP, describing him as “a legend in many, many ways.” Hilary Benn, who has described himself as “a Benn, not a Bennite”, said Mr Burnham offered a “combination of vision, determination and a great ability to communicate.”

He rejected the idea of a plot to oust Mr Corbyn if the veteran left-winger wins the leadership. “We should respect all of the candidates and our members for the decision they will soon make,” he said. “But we also have to recognise that choosing Labour’s next leader is a big responsibility with big implications for our party and the country.”

However, Mr Burnham suffered a setback when the Unison trade union nominated Mr Corbyn and named Yvette Cooper as its second choice, boosting her prospects of emerging as the “stop Corbyn” candidate.

Mr Burnham, the shadow Health Secretary, had hopes of winning Unison after his long campaign against “NHS privatisation.” The union has thousands of members working in the NHS.

Polls of Labour members and supporters entitled to vote in the contest have put Mr Corbyn in the lead. But last night the Burnham camp released its canvassing figures, showing Mr Burnham on 37 per cent, Mr Corbyn on 28 per cent, Ms Cooper on 10 per cent and Ms Kendall on 6 per cent, with 20 per cent replying “don’t know.” Ms Cooper’s allies hit back by claiming she was at least level with Mr Corbyn and well ahead of Mr Burnham.

Dave Prentis, Unison’s general secretary, said: "Jeremy Corbyn's message has resonated with public sector workers who have suffered years of pay freezes, redundancies with too many having to work more for less.”

Unison has 1.3m members, 28,000 of whom are members of the Labour Party, with another 15,000 registered to vote in the leadership contest as affiliated members. Under Labour’s new rules, unions no longer command a third of the votes in the Labour election. Their members vote individually and do not have to follow their leaders’ recommendation.

Mr Corbyn said: “Unison members are in the frontline of the impact of the Government's austerity agenda. They are the people that provide the services our society relies on. They should be valued and heard. As leader of leader of the Labour Party, I would promote high-quality, modern, public services - against outsourcing, privatisation and low pay.”

In an interview with the New Statesman magazine, Mr Corbyn said that if he became prime minister, he would want to pull Britain out of Nato as well as scrap the Trident nuclear weapons system. Although he is a republican, he said abolition of the monarchy would wait because “my priority is social justice.” He backed the removal of the charitable status of independent, fee-paying schools and would force state-funded academies and free schools to return to local authority control.

Mr Corbyn dismissed speculation that he might stand down if he won the leadership, saying he would be “in it for the long run... I hope the party would want to hold together and I'm sure it would.”