New Haven has an unwritten rule — the “no-freeze policy” — that anyone, provided he or she is sober, is guaranteed shelter for the night.

But members of the Yale Hunger and Homeless Action Project said they are observing a rising number of homeless people turned away from shelters, contrary to the city’s promise. The group is rallying its members to write letters to the mayor and other city officials requesting that the city take action to curb what the group sees as a growing crisis.

Respect Line, which is part of YHHAP, has recorded a rising number of homeless turned away from shelters, said Diana Cieslak ’04, a YHHAP co-coordinator. On March 26, Immanuel Baptist Shelter, Columbus House and the Overflow — three of New Haven’s shelters — turned away six people, according to YHHAP’s numbers.

The following night, Cieslak said, those same three shelters turned away 12 people. In a letter to the mayor and other city officials, YHHAP members wrote that without Respect Line’s assistance, at least 18 people would have been forced to sleep outside last week.

But city officials said that no one who is eligible has been turned away.

John Huettner, the special projects director for the city’s Community Services Agency, said that he talks regularly with the staff running the shelters funded by the city and that he has yet to hear of people being turned away and unable to find shelter anywhere. He said the city’s contingency plan encourages shelters to communicate with one another so that if one is full people can be shifted to another.

Huettner said one of the city’s primary concerns is that 30 percent of the people checking in to New Haven’s shelters are not city residents.

“The city is not totally responsible for this [crowding],” Huettner said. “Many towns, because they don’t provide services, dump their residents on New Haven.”

YHHAP wants to encourage the city to improve shelter staff training, formalize the no-freeze policy through an ordinance from the Board of Aldermen, use a portion of its contingency money for adding new beds and expand the no-freeze policy to include those who are not sober when seeking shelter.

In the six out of the last 12 nights, the Columbus House overflow shelter has been at or beyond capacity, said Alison Cunningham, Columbus House’s executive director. When necessary, she added, the shelter is willing to set up extra cots to expand the 75-person capacity in its overflow facility.

“The numbers just keep on rising from day to day, week to week,” Cieslak said.