Attorney General Martha Coakley this week announced a discrimination lawsuit against Peggy O’Neil’s, a Dorchester Avenue bar, accusing the establishment of a “pattern of not allowing customers of color to enter and use the bar.” The pub’s co-owner and her sister staunchly rejected the charges, chalking one of them up to a misunderstanding and another to one of the group members having had too much to drink.

Announced on Monday, the lawsuit alleges that in the first of three incidents, two men of Cape Verdean and African-American descent waited in line in Dec. 2010 as bar staff let Caucasian patrons head inside. Caron O’Neil, an owner of the bar, is said to have told the group, “This is your first time here, huh?” She later told them she didn’t “want any trouble” and she didn’t know them, and they should go somewhere else. At the same time, Caucasian customers were allowed inside, the nine-page lawsuit says.

In another incident, a second group, made up of Cape Verdeans, Hispanics, and African-Americans, was also not allowed to enter the bar, the lawsuit alleges. O’Neil is said to have told them, “You don’t look like the type of people” the owner would know and “we don’t like people of your kind here.”

Earlier this year, in April, a third group of people of color was rejected at the door, according to the lawsuit.

Dorchester locals sometimes call the bar “the 1310,” in a reference to its location on Dorchester Ave. The pub, which used to be known as “Glass Top Lounge,” has a 2 a.m. closing time and a capacity of 221.

Caron O’Neil told the Reporter the bar has been in business since 1963 and they have never had a discrimination complaint. “I absolutely do not discriminate,” O’Neil said. Tracy O’Neil, who co-owns the bar with her sister, maintained in a separate interview that the charges are untrue. “We do not discriminate against anybody,” she said, adding that her sister is gay. “I believe it was a misunderstanding. I believe one of the people had an out-of-state license,” she said, noting further that one of the prospective customers started swearing because they had to wait in line.

“I have Spanish, I have African-American, Chinese, Vietnamese customers; I have an array of customers,” said Tracy O’Neil, who works during the day. “We are in a very diverse neighborhood and have very diverse customers.”

The attorney general’s lawsuit seeks monetary damages, civil penalties, and a preliminary injunction requiring the bar’s staff to comply with state and federal anti-discrimination and consumer protection laws, and undergo anti-discrimination training.

In the encounter in April of this year, a group of three black women and a Caucasian man went to O’Neil’s after starting at the Banshee Pub, according to the lawsuit. As they were waiting in line, Caron O’Neil allegedly approached them and told them they could not enter because she did not recognize them and they were not regular customers, the suit maintains.

One of the woman claimed she was being discriminated against, and O’Neil told her to take her “racial [expletive]” elsewhere, according to the suit. As the argument grew heated, a detail officer on duty nearby, an African-American, was called over and instructed the black woman to leave.

O’Neil said the woman was argumentative and had too much to drink. “She didn’t respect anybody,” O’Neil told the Reporter.

“We allege that Peggy O’Neil’s engaged in discriminatory and unlawful conduct,” Coakley said in a statement. “No one who lives, works, or visits Massachusetts should be subjected to discrimination. All businesses must ensure that appropriate anti-discrimination policies are posted and adhered to within their establishments.”

Separately, Caron O’Neil went before the Boston Licensing Board on Tuesday for a fight that broke out in the bar on June 26. Security personnel intervened and escorted the patrons out. At the board’s hearing on the matter, police said the pub had cooperated fully and there was little the bar’s management could have done differently.

The bar has been involved in a number of incidents on and near its property over the years, including two separate accusations of an assault and battery of an employee on a patron in 2009 and 2010, according to a review of records on file with the Licensing Board.

Correspondent Adam Gaffin contributed to this report.