A battle between two unions that represent nurses in New York is heating up, with each side accusing the other of raiding its membership rolls.

The New York State Nurses Association, which represents 36,000 registered nurses statewide, said 1199 SEIU has mounted a campaign in recent months to convince nurses to switch affiliations with tactics such as roaming hospitals to recruit new members, mostly during the night shift. Most recently, the union alleged, 1199 members ambushed its nurses at Peninsula Hospital Center in Queens, where nurses voted in May in favor of new representation. “It’s a campaign of seduction and it’s a campaign of deceit and it’s what they do best,” the New York State Nurses Association’s director of collective bargaining, Lorraine Seidel, said on Friday.

Officials at 1199 SEIU, which represents 6,000 New York City nurses, said the opposite is true. Nurses at Peninsula sought 1199 representation on their own, they said. Further, they said the New York union has affiliated itself with a national union, the California Nurses Association/National Nurses Organizing Committee, an 80,000-member group that has clashed with the Service Employees International Union in recent months — particularly in Ohio, where SEIU accused it of “union busting.” The New York union said the two are not affiliated.

In New York, 1199 officials said, the California Nurses Association recently began distributing anti-SEIU leaflets at hospitals including St. Barnabas Hospital in the Bronx. “They are raiding SEIU hospitals in West Virginia, Iowa, they’re all over,” 1199 SEIU’s organizing director, Amy Gladstein, said. Rejecting allegations that her organization was doing the same, she said, “We have nurses all the time, calling 1199 and saying they want to be part of 1199.”

At stake is the membership of thousands of nurses throughout the state and country. 1199 SEIU and its umbrella organization, the Service Employees International Union, have openly said the union seeks to unify all unionized nurses as part of an effort to some day organize nonunion nurses. The New York State Nurses Association seeks to remain a nurses-only group. “We certainly didn’t want to be swallowed up by a union of pot men, janitors,” Ms. Seidel said.

It is not the first time SEIU has been accused of heavy-handed tactics. In April, the California Nurses Association accused SEIU members of physically assaulting some of its members at a labor conference in Michigan. Subsequently, a California Superior Court issued a temporary restraining order to prevent the union and its president, Andy Stern, from stalking and harassing members of the California-based union. SEIU officials at the time presented a different account of the incident, and said no conference attendees were assaulted.

Even as the dispute escalated in New York, SEIU members attending the union’s conference in Puerto Rico this week passed a no-raid resolution in response to the conflict with the California Nurses Association.

Officials at the New York State Nurses Association questioned the integrity of the resolution, which coincides with discrete — and overt — campaigns to bring on new nurse members.

Officials from 1199 flatly denied that account. “While they are on that page, when their nurses come to us and say they want a different kind of representation, we’re going to answer that call,” Ms. Gladstein said.