Ivan Scalfarotto, 49, said in his blog he was aiming to force discussion of the issue into the mainstream and rally the support of "all those people of good faith who have been thinking up until now that it was enough just to wait."
"Between the demonstrations of Catholic fundamentalists and the Gay Pride marches, you'd think there was nothing in between," wrote the minister, who is gay himself and a long-standing rights campaigner.
"The time has come to do something more to support those working to ensure Italy finally catches up with Kentucky, or at least gets near," he added in a reference to the recent US Supreme Court ruling which forces even the most conservative of states to allow gay marriage.
Italy stands alone amongst major western Europe states in having no provisions for the official recognition of homosexual couples. Draft legislation that would authorise civil unions for them is currently blocked in the Senate.
He said he would continue not eating until there was "certainty on the date when this grave violation of human rights will end."
Thousands of amendments have been put forward by opponents of the bill who include members of one of the governing parties, the New Centre Right (NCD).
The junior partner in Prime Minister Matteo Renzi's coalition is not opposed to civil unions in principle but is demanding the removal of a provision that would allow gays to adopt the children of their partners and another one on the transfer of pension rights upon the death of one of the partners.
Hundreds of thousands of people marched in Rome on June 20th to voice their opposition to the proposed law but recent opinion polls have indicated a majority of voters favour reform, with support for civil unions and gay marriage having risen significantly after Ireland voted strongly in favour of allowing same sex couples to wed.