The invasion of Iraq is a bigger disaster than the Vietnam war, and Prime Minister Tony Blair (search) should have resigned for making a false case for intervention, former Foreign Secretary Malcolm Rifkind (search) said Wednesday.

"Here we actually went in, created a war that would otherwise not have occurred and now we see a complete political vacuum," Rifkind said on British Broadcasting Corp. TV.

Blair, who based the case for war on claims that Iraq was building stockpiles of weapons of mass destruction, should have resigned "the moment it became clear that he had misrepresented [to] Parliament, abused the intelligence agencies," Rifkind said.

"No prime minister who has gone to war on a false prospectus — whatever good faith he may or may not have had — should remain in office when it turns out to be the single biggest foreign policy disaster this country has known since the war," he said.

Rifkind, who served as foreign secretary in 1995-97, is now a candidate for leader of the opposition Conservative Party (search).

Rifkind did not call for a swift withdrawal of British forces.

"It is precisely because we have no moral authority to be there in the first place that we can't just cut and run, if that brings even more suffering to the Iraqi people," he said.

Although Rifkind drew a comparison to the Vietnam War, Britain declined to contribute troops to support the United States in that conflict.