Updated

Massachusetts lawmakers are threatening to boycott a St. Patrick’s Day parade after the organizers appeared to exclude a gay veterans group – the latest controversy surrounding the inclusion of gay groups in traditionally Catholic parades.

The Allied War Veterans Council of South Boston voted to exclude the group OutVets from the parade, The Boston Globe reported. The 9-4 vote was contentious even within the council, with the parade marshal resigning over the vote.

The council released a statement Friday saying that the group was not banned, but the issue was over the rainbow flag on the group's logo.

"Firstly, OutVets has not been officially notified that they will not be allowed to march in the Parade," the statement said. "OutVets was informed that our Code of Conduct prohibits 'the advertisement or display of one’s sexual orientation,' and that the 'rainbow' flag on its banners and logo was in violation of this rule."

"The question at hand is not one of inclusion or discrimination," the statement said. "The Council is accepting of all people and organizations, but it will not permit messages that conflict with the overall theme of the Parade."

OutVets marched in the parade in 2016 and 2015, after the council reversed a decades-long ban on gay groups from marching in the parade.

The apparent exclusion of the group has caused sponsors as well as a wide-range of lawmakers to pull their support from the parade. Boston Mayor Martin Walsh, Republican Gov. Charlie Baker, Sen. Edward Markey, D-Mass., and Rep. Seth Moulton, D-Mass., all pledged to boycott the event.

"It is outrageous and disgraceful that a group by the name of Allied War Veterans would decide to ban OutVets from marching in this year's St. Patrick's Day Parade," Moulton, himself a veteran, told MassLive.com.

“I will not tolerate discrimination in our city of any form. We are one Boston, which means we are a fully inclusive city,” Mayor Walsh said in a statement. “I will not be marching in the parade unless this is resolved. Anyone who values what our city stands for should do the same.”

The Allied War Veterans Council did not respond to a request for comment from Fox News, but The Associated Press reported that it had scheduled an emergency meeting to reconsider the vote.

The controversy over Boston’s parade echoes a similar years-long controversy over the St. Patrick’s Day Parade in New York City, where Catholic groups sparred with gay-rights group for years over the ability to prohibit explicitly gay groups from marching.

Parade organizers softened its ban in 2016, allowing two groups to march, after first allowing an NBCUniversal float in 2015.

The South Boston parade, in the south of the city, starts at Gillette Stadium and ends near the Dorchester Heights National memorial.

The Associated Press contributed to this report.