New York's St Patrick's Day parade on Tuesday allowed a solitary gay group to march openly for the first time in its 254-year history but faced fresh accusations of not being more inclusive.

City officials, including New York Mayor Bill de Blasio who swept into office in 2014 on a progressive platform, said they would not join Manhattan's festive celebration of the Irish American community until other gay groups are allowed to march freely.

OUT@NBCUniversal, which calls itself an employee resource group for LGBT and Straight Ally employees at NBCUniversal, was the only gay group scheduled to join the colorful and festive parade.

Its inclusion allowed Irish brewery Guinness, which refused to sponsor the parade in 2014 because of the ban on gay groups, to resume their sponsorship this year.

Social media posts showed activists protesting alongside Tuesday's parade, holding up banners saying "Let Irish Gays into Irish Parade! and "What Would Jesus Do? Let Irish Gays March Too!"

The group Irish Queers and allied activists praised the mayor for not attending and condemned the exclusion of other Irish gay, lesbian and transgender groups.

"There is no logic to letting OUT@NBC march except as another way to keep Irish LGBTQ groups out," said Gaby Cryan of Irish Queers.

"The parade organizers have claimed a right to discriminate against us because they're running it as a Catholic procession."

De Blasio joined other officials in taking part in the St Pat's for All parade in New York's borough of Queens earlier this month.

But local reporters said he stuck to his customary tardiness by turning up 15 minutes late for a special mass Tuesday presided over by Cardinal Timothy Dolan, grand marshal of the parade.

The first St Patrick's Day parade in New York took place on March 17, 1762 -- 14 years before the Declaration of Independence.

Organizers say it is the oldest and largest parade in the country.