DAVID Miliband, the brother of the Labour leader, warned a packed audience in Cambridge that the political left may be ideologically strong but its weakness lies in policies.

Speaking to the Cambridge Union society, Mr Miliband, who lost out to his brother Ed in the Labour Party leadership contest in 2010, said the left is facing a crisis in Europe as austerity politics favours the centre-right.

Mr Miliband, foreign secretary under Gordon Brown, spoke mainly on international issues but answering a question on his brother's leadership, he said: "He is the right person as he won the [leadership] election. He is playing the long game and standing up for what he believes in and that is the right thing to do.

"He is leading the party and speaking with convictions - he is not playing tactically."

The MP for South Shields then addressed the political state of the Labour party: "The left is now strong philosophically but has a weakness in policy.

"The danger is the populism on the right in times of austerity."

During the first 20 minutes of Mr Miliband's appearance he answered questions from Professor Andrew Gamble, head of the POLIS Department at Cambridge University, before taking questions from the floor.

Before touching on issues in North Korea, the Eurozone, Syria and Libya, Mr Miliband called for "engagement" with Iran on its nuclear programme.

"My own view is that it would be very dangerous indeed for Iran to become a nuclear state but it would be as dangerous to begin an attack on Iran," he said.

"I am convinced that the Iran will not halt it's nuclear programme under the pressure of sanctions. You need engagement with all levels of Iranian society."

He also cited the four main focuses shaping the world today as a surge in civilian politics, a "shift from resource plenty to resource scarcity", the rise of political islam and a shift of power from West to East.

Answering a question on Britain's position in Europe he warned a of a "club within a club" which Britain would not be part of and would have to follow the lead rather than take it.

"In other issues like foreign policy alliances, we will become toxic," he said.