Missing him already: Labour mourns David Miliband’s departure

David Miliband's resignation from parliament is being greeted with dismay by Labour politicians in Westminster, as they confront the prospect of Ed Miliband becoming the senior Miliband brother in the Commons.

The man Labour party's members and MPs chose to be their leader – Ed Miliband only emerged on top after the votes of trade unions were included – once again demonstrated his attractiveness to his colleagues after announcing his intention to become head of the International Rescue Committee charity in New York.

A theme was detectable among Labour backbenchers responding to the news on Twitter. Steve Reed tweeted he was pleased for David Miliband for having "landed a job that will mean so much, but what a giant loss for Labour".

Keith Vaz said he was "stunned" by the news and lamented "the best and the brightest leaving the country", adding the news was a "huge loss to British politics".

Mike Gapes, the former foreign affairs committee chair, wished David Miliband well and said he was a "big loss to Labour".

Tony Blair, who took on David Miliband as his head of policy while preparing for his 1997 landslide victory, continued the theme by saying Miliband's departure was "obviously a massive loss to UK politics".

"I congratulate David on his appointment to a major international position. It shows the huge regard in which David is held worldwide," the former prime minister said.

"He was the head of my policy unit and then a truly distinguished minister in the government and remains one of the most capable progressive thinkers and leaders globally. I hope and believe this is time out not time over."

Ed Miliband made clear he hoped his elder brother could make a "contribution" to public life at some stage in the future.

"As for us, we went through a difficult leadership contest but time has helped to heal that," he said.

"I will miss him. But although he is moving to America, I know he will always be there to offer support and advice when I need it."