In a one-off comeback speech in New York, which broke a medical ban on speaking in public, the former Conservative Prime Minister attacked those who use environmentalism, feminism and human rights campaigns to fight capitalism and the nation state.

She praised Tony Blair, but above all President Bush, for overriding the “rot” that “paralysed” the United Nations.

Baroness Thatcher was speaking at a meeting of Atlantic Bridge, an Anglo-US free market think-tank set up by Liam Fox, the Shadow Health Secretary. Her audience included Michael Ancram, the deputy leader of the Conservative Party, and Michael Howard, the Shadow Chancellor.

Dr Fox said: “The fact that Michael Ancram and Michael Howard are both here as well is symptomatic of a resurgence of confidence on the Right. An intellectual renaissance took the Republicans back to power and this is a reflection of us reinvigorating the Conservative Party.”

Lady Thatcher said: “For years, many governments played down the threats of Islamic revolution, turned a blind eye to international terrorism and accepted the development of weaponry of mass destruction. Indeed, some politicians were happy to go further, collaborating with the self-proclaimed enemies of the West for their own short-term gain — but enough about the French. So deep had the rot set in that the UN security council itself was paralysed.”

She spoke of her pride at the way Britain stood by America over Iraq: “Our own Prime Minister was staunch and our forces were superb. But, above, all, it is President Bush who deserves the credit for victory.”

Lady Thatcher said that she had “drunk deep from the same well of ideas” as her great ally, the former US President Ronald Reagan. Both instinctively knew what worked, she said, including low taxes, small government and enterprise. “We knew, too, what did not work, namely socialism in every shape or form. Nowadays socialism is more often dressed up as environmentalism, feminism, or international concern for human rights. All sound good in the abstract.

“But scratch the surface and you will as likely as not discover anti-capitalism, patronising and distorting quotas, and intrusions upon the sovereignty and democracy of nations.”

Lady Thatcher warned that America and Britain faced “a pervasive culture of anti-Westernism" that needed to be challenged. "There are too many people who imagine that there is something sophisticated about always believing the best of those who hate your country, and the worst of those who defend it."

Dr Fox said that the time was ripe for the Conservatives and Republicans to rebuild their ideological links in all areas of policy. "Tony Blair has established himself as an ally of George Bush but Labour has not forged a link with America," he said. "Their relationship is limited purely to foreign policy.

"There is a heightened awareness of the importance of the Anglo-American link and that this is the most natural state of alliance for the UK."

"Margaret Thatcher embodies the strength of that alliance and probably represents the high point of co-operation, not just on a practical sense but in terms of philosophical alignment. The world may not see her like again for many years to come."

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