Colleagues of former foreign secretary David Miliband today described his departure as a great loss to the Labour Party after he announced he is moving across the Atlantic.

In a letter to his constituency party chairman in South Shields, 47-year-old David - who was long regarded as the brightest Labour star of his generation and the party's most likely future prime minister - said he was quitting as an MP and moving to New York.

He said it was 'very difficult' for him to be leaving politics in the UK as he takes up the position of president and chief executive of the International Rescue Committee.

His departure comes two-and-a-half years after the bruising Labour leadership battle where he lost by a whisker to his brother Ed on the back of trade union votes.

Former Labour leader of Norwich City Council Steve Morphew, who got to know David Miliband when he was working at the Department for Communities and Local Government, said he was a great party activist.

But he also said the former cabinet minister would be missed for his community work and his ground-breaking Movement for Change organisation, which champions a new grassroots approach to politics.

David Miliband visited Norwich in 2010 to campaign against plans to switch off street lights and also visited the city last year where he visited a school and the university.

Mr Morphew said: 'He likes Norwich as a place. We are a bit of a magnet for Miliband.'

He added: 'It is a shame he is leaving, but I cannot imagine that he will disappear as an influence. I rather suspect he will be back in a few years. International experience will serve him well for a return to Britain.'

Former home secretary and Norwich North MP Charles Clarke also praised the former cabinet member's 'massive contribution' to both the country and the Labour party.

He said: 'He will be a major force for positive change and he will be greatly missed.'

Jess Asato, Labour's prospective parliamentary candidate for Norwich North, worked with David Miliband on his leadership campaign.

She said: 'He will be a huge loss to the Labour Party, but our loss is the gain of millions of the poorest people in the world.'

She said: 'He has taught me that at the end of the day politicians have to remain about the values and the people they came into politics to serve. You can have setbacks, but that doesn't mean you cannot achieve the things that you set out to achieve.

When David Miliband visited Norwich last year he said the lack of Labour seats in the region was 'very dangerous' and stressed the need to re-build.

Ed Miliband said British politics will be 'a poorer place' without his brother and admitted that the leadership contest had been 'difficult', but added: 'Time has helped to heal that. I will miss him.'