Luiz Inacio Lula da Silva also questioned why some politicians oppose gay rights but still take gay people's taxes and votes.
The President said he is in favour of civil unions.
"We must stop this hypocrisy because we know they exist," he said in an interview with a TV station.
"There are men living with men, women living with women, and many times they live extraordinarily well.
"They build a life together, they work together and I am favourable."
The President, universally known as Lula, attacked opponents of gay rights.
"One thing that amazes me is why politicians who are against do not refuse their votes, why Brazil does not refuse their income tax.
"The important thing is for them to be Brazilian citizens, for them to be committed to the nation. I support the civil union."
He said that Congress was working on the issue.
Homosexuality has been legal in Brazil since 1823 and civil unions are allowed in some areas.
However, homophobia and gay-bashing remain significant problems in the country of 184 million people.
In June Lula became the first nation leader to launch a conference with the sole purpose of promoting gay equality, where he announced his support for gay rights, and stated he will "do all that is possible so that the criminalisation of homophobia and the civil union may be approved."
A proposal granting same-sex couples the same rights as married heterosexuals has stalled in Brazil's Congress for more than 10 years, prompting some states to take their own action.
Southern Rio Grande do Sul state has permitted same-sex civil unions since 2004, and a Sao Paulo state court allowed a gay couple to adopt a 5-year-old girl in late 2006.
Rio de Janerio grants the same benefits to the same-sex partners of state employees.
The country's Constitution refers to marriage as between a man and a woman, and marriage is a federal issue, though states may choose to recognise civil unions or other de facto same-sex relationships.
A series of court rulings have given gay and lesbian couples some rights in areas such as immigration, welfare, pensions and inheritance.