Tony Blair has issued a rallying cry to the world's richest countries to help the poorest by cutting trade barriers.
In a speech at the Guildhall in London, the prime minister announced the UK was to treble the amount it made available for trade aid in the next five years.
Ahead of global trade talks he urged the US and the EU to match this amount.
But shadow trade and industry secretary David Willetts said Mr Blair was giving "lofty speeches" and missing a valuable opportunity to reduce trade subsidies.
Mr Blair also urged concessions on farm subsidies and tariffs to "break the logjam" threatening the talks.
In return, developing countries must open up to foreign investment, he told the Lord Mayor of London's banquet.
Reducing world poverty would help fight terrorism, Mr Blair added.
He said: "In a modern world there is no security or prosperity at home unless we deal with the global challenges of conflict, terrorism, climate change and poverty.
"Self interest and mutual interest are inextricably linked. National interests can best be advanced through collective action.
"Calculate not just the human misery of the poor themselves.
"Calculate our loss: the aid, the lost opportunity to trade, the short-term consequences of the multiple conflicts; the long-term consequences on the attitude to the wealthy world of injustice and abject deprivation amongst the poor.
"We will reap what we sow; live with what we do not act to change."
But Mr Willetts told BBC Radio 4's Today programme the prime minister had given a "similar" speech to the European Parliament in July.
"It's the implementation, it's the follow-up, it's the gritty practicality that's missing with him, and sadly we're seeing this weakness as we go into the Hong Kong trade negotiations in the next few weeks," he said.
The Tory MP said Europe's name was "morally damaged" by the effect of its agricultural subsidies on the poorest countries and he believed there was a "powerful moral case" for free trade.
Mr Willetts said that while the UK held the EU presidency, Mr Blair should "play his hand much more strongly" so the EU adopted a free trade position in Hong Kong, which would include reducing agricultural subsidies.
Peter Mandelson, in his position as EU Trade Commissioner, must "take the lead" in pressing for the reduction in these subsidies, he added.
The World Trade Organisation gathering starts on 13 December, with fears growing that the pronouncements made on poverty by G8 leaders at Gleneagles in July may not result in a meaningful deal.
Despite offers from major players like the US and EU to consider reductions in agricultural subsidies and tariffs in order to open up markets to poorer nations, negotiators have so far held back from the kind of breakthrough sought by anti-poverty campaigners.
Mr Blair said: "We need a comprehensive, ambitious agreement to cut barriers to trade in the three key areas: agriculture, non-agricultural market access, and services."
Specific measures to help the poorest countries, he argued, should include doubling investment in infrastructure and eliminating all export subsidies.
Rules applied to exports from the poorest developing countries should be simplified, he added.
The Hong Kong summit comes at the end of Mr Blair's year-long presidency of the G8.