Hague turns his sights on the Left.
Mr Hague was speaking at the beginning of the Republican Party Convention in Philadelphia, where Senator George W Bush is expected to be endorsed as the party's presidential candidate.
The Tory leader was speaking to members of the International Democrat Union, a gathering of centre-right leaders from around the world.
Mr Hague said that while it was time to lay down their arms in the fight against Communism, parties of the centre-right faced a new challenge.
While they had exposed the bankruptcy of socialism, too many of the centre- right parties had lost battles in their own backyards, he said.
Although he did not mention Mr Tony Blair or Mr Bill Clinton by name, his speech was seen as a clear attack on the Labour Party and the US Democrats.
"Perhaps because our victory over the old left was so complete, we allowed ourselves to become complacent," he told delegates.
"We were slow to see that the left was re-inventing itself. They disowned their roots, repackaged themselves and chose new political leaders.
"They made a systematic attempt to occupy the centre ground of politics by imitating our language, adopting our issues and pretending to be parties of the right. Our Republican Party hosts know all too well who pioneered this."
Mr Hague denounced this left wing "repackaging" as a fraud, stating that their actions rarely matched their rhetoric.
Mr Hague praised Governor Bush for "making compassion part of the conservative lexicon in the United States" claiming that it was the policies of the right which delivered a more compassionate and fair society.