A new state civil unions law has failed to ensure that same-sex couples in New Jersey enjoy the same rights as married heterosexuals, an official report said on Tuesday.

On the first anniversary of the law's implementation, the Civil Union Review Commission said some employers in New Jersey have refused to provide benefits to the partner of employees in a civil union.

New Jersey last year became the third state to pass a civil unions law after its Supreme Court affirmed that same-sex couples have the same rights as heterosexual couples, but left the state legislature to decide whether to enshrine those rights in an institution called marriage.

Lawmakers opted for civil unions, to the dismay of gay-rights activists who argued that true equality can only be achieved by allowing gays and lesbians to marry.

In Massachusetts, the only state to have legalized same-sex marriage, the law prompted many employers to provide equal benefits to same-sex partners, the report said.

The panel of official and legislative appointees established as part of the law blamed the failure of some New Jersey employers to recognize civil unions on a federal law that allows self-insured companies -- an estimated 50 percent of all employers in the state -- to choose not to offer benefits to same-sex partners.

In addition, the federal Defense of Marriage Act says any federal statute or regulation that provides benefits to spouses applies only to partnerships between one man and one woman.

Steven Goldstein, chair of Garden State Equality, a leading gay-rights group in the state, said about 2,500 New Jersey couples have formed civil unions since the law was passed, and about a fifth have complained to his group that their unions have not been recognized by employers.