Labour leader Miliband joined in praise for the work that Southampton politician and humanitarian worker Del Singh, a Labour MEP candidate, had done in helping people in need across the world.
He said: “My thoughts - and the thoughts of the whole Labour Party - are with the family and friends of Del Singh who was killed in yesterday's tragic suicide bomb in Kabul.
“People everywhere will be appalled and shocked by this barbarous act of terror deliberately targeting members of the international community living and working in Kabul in the service of the Afghan people.
“Del spent over ten years carrying out vital work on development projects in Afghanistan, Kosovo, Sudan, Sierra Leone and other countries.
“He dedicated his life to working with people across the world who needed his support.”
Labour's General Secretary Ian McNicol added: “Del Singh was a committed and passionate campaigner who wanted to improve the lives of people in conflict zones and those of people closer to home.
“Del will be missed by everyone in the Labour Party who has worked and campaigned alongside him for over two decades. Our thoughts are with his family at this sad time.”
Other senior politicians voiced their thoughts through Twitter.
Labour deputy leader and shadow culture secretary Harriet Harman said: “Shocked & saddened Del Singh , below, killed in Kabul suicide bombing.
"My deepest sympathy with his family and friends.”
Chuka Umunna, below, Shadow Business Secretary, said: “Shocked and so sad to hear of the death of our MEP candidate, Del Singh, in Kabul.
“Del was such a lovely and dedicated guy. RIP Del.”
Shadow foreign secretary Douglas Alexander, below, said: “Deeply saddened by the cowardly murder of Del Singh in Kabul - an aid worker, a Labour candidate, and a passionate campaigner for justice.”
Margaret Curran, Labour's Shadow Secretary of State for Scotland, said: “Have just heard of tragic death of Del Singh in Kabul.
“Huge loss in fight against poverty - sincere condolences to family and friends.”
Shadow home office minister Steve Reed MP said: “Shocked to hear of the death of Labour European candidate Del Singh in a Taliban attack in Kabul. Such a lovely man, such a waste of life.”