Per Ahlmark claims in his book "Gör inga dumheter medan jag är död!" (literally: "Don't do anything stupid while I am dead") that he was told by current Liberal Party leader Jan Björklund that Bildt forbade ministers to use the term "genocide" when talking about the killing in Darfur.
"Ministers, even the so-called liberals, sheepishly followed Bildt's directions," wrote Ahlmark.
Björklund was unwilling on Monday to discuss the revelations with news agency TT.
While the definition of what constitutes genocide is a matter for discussion on a case-by-case basis, US Secretary of State Colin Powell used the term in 2004 as the UN Security Council prepared to debate a second resolution threatening sanctions on Sudan.
"There is always a discussion about this, even while the killing goes on. It becomes a genocide when sufficient powerful people - such as Colin Powell - call it as such," Sudan expert Shane Quinn told The Local on Monday.
Ahlmark continued to accuse the four Alliance party leaders for having fooled the voters in 2006 by declining to reveal that Carl Bildt was slated to become foreign minister.
"The oil man with the share options will, we thoughtlessly believed, remain in north Africa and build up his private wealth. It was thus fully possible to vote for the Alliance in 2006 and hope for the best. They fooled us," Ahlmark wrote.
He furthermore slammed Bildt for his record on Israel, criticising him for being "ignorant and horribly cold on the Jews".
Ahlmark was part of a group who in 1991 pushed for a court case against the anti-Semitic radio station Radio Islam, and sought to meet the party leaders prior to the election of that year to discuss a perceived increase in anti-Semitism.
The group were able to secure an audience with representatives from the Social Democrats, the Liberal Party (Folkpartiet), the Centre Party and the Christian Democrats.
But not Carl Bildt, who was Moderate Party leader at the time.
"Instead he let it be known in a demeaning manner that he was himself totally disinterested in facts about contemporary, anti-Jewish sentiment," Ahlmark wrote.
Ahlmark continued to criticise Bildt for having a "simple-minded" view on the state of Israel as a mono-ethnic country, despite the fact that it is home to people from more than 100 different countries.
"The foreign minister's ignorance of this country's history, culture, vitality and democracy is tangible and is based on a clearly hostile attitude," he wrote, adding that this was evidence of Bildt's "reactionary values".
"We have no comment on this," Anna Charlotte Johansson, Carl Bildt's press secretary, told The Local from New York where the foreign minister is due to visit the UN General Assembly.