The appeal came Tuesday on the campaign's 5th anniversary celebrations at the House of Lords, Britain's upper house of parliament.
"I am pleased to see that our campaign for UN recognition of International Widows Day is gaining support from all over the world and call upon the UN to bestow official recognition accordingly," Blair said.
She made the appeal as president of the Loomba Trust, the global charity that was founded by Indian-origin industrialist Raj Loomba to alleviate the plight of impoverished widows and their children.
"Poverty is the curse of mankind, but when you put it in the context of widows and their children, it creates a new dimension in inhumanity," said Loomba.
The event's objective is to raise awareness of the deprivations faced by more than 100 million widows worldwide caught in the extreme poverty trap - starvation, HIV, rape, conflict, sexual slavery and social injustice.
Another 100 million widows' children die before their fifth birthday every year.
Lord Navneet Dholakia of the Liberal Democrat party hosted the event, which was attended by Sir Richard Stagg, the British High Commissioner to India, his wife Lady Arabella, and veteran broadcaster and journalist Sir Mark Tully, among others.
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