He said civil partnerships did not go far enough and parental rights of gay parents need to be reformed.
“A democratic republic that professes a commitment to the principle of equal citizenship should not continue to prevent same-sex couples from entering into a legal partnership that is legally recognised and designated as being a marriage,” Mr Shatter said as he launched a report by the Gay and Lesbian Equality Network.
Mr Shatter said issues connected with parental rights of gay parents would be modernised in upcoming legislation.
The Constitutional Convention will discuss the issue of same-sex marriage in April.