David Miliband is likely to step down as MP in order to take up a role in New York-based charity, say reports.
The former foreign secretary and the brother of Labour leader Ed Miliband is expected to announce his surprise decision later in the day.
According to the Daily Mirror, Miliband intends to step down immediately from British frontline politics to become head the New York-based International Rescue Committee, a charity working on humanitarian crisis across the world. The role is said to be his "dream job."
"David has landed a dream job in charge of a charity in New York and wants to take it. But it means leaving politics," the source told the Mirror.
A close friend of Miliband has also confirmed the impending resignation to the BBC. This will also bring an end to what Miliband called as "daily soap opera" and "psychodrama" between the two brothers.
One friend told the Guardian, "David was always clear that it was time for him to make a decision this year about his future. The feeling was that if he came back into the shadow cabinet it would be a permanent pantomime. But equally if he did not come back, but remained in the PLP [parliamentary Labour party], it would also be a permanent pantomime. It was therefore not sustainable."
Miliband was beaten to the Labour party leadership two years back by his brother and the resignation announcement is likely to come as huge setback to the right of the party. The election created a rift between the brothers and David Miliband refused to serve in Ed Miliband's shadow cabinet.
There was widespread speculation that the 47-year old would return to opposition frontbench earlier. Many Labour leaders hoped Miliband would return to the shadow cabinet before the 2015 general election.
Labour leaders have expressed shock over the news. Leicester East MP and chairman of the Home Affairs Select Committee, Keith Vaz wrote on twitter, "Stunned by the news about David Miliband. A huge loss to British politics. The best and the brightest leaving the country."
John Woodcock, MP for Barrow and Furness said in his twitter account, "David will be brilliant over the water as he always is. He's an inspiration; know he'll be back in fight one day but for tonight am just sad."
Conservative Party Chairman Grant Shapps said Miliband "has contributed a great deal to British politics and we wish him well."
Miliband's resignation will trigger a by-election in South Shields, a seat which he has been holding since 2001. The by-election in the safe Labour constituency is likely to take place in May.
Miliband is married to American violinist Louise Shackelton and the couple has adopted two children.