Cambridge mayor Francis H. Duehay '55 protested proposed cuts of Housing and Urban Development funds in a letter mailed Tuesday to President Reagan.

Focusing on potential cutbacks in the Community Development Block (CDB) Grant program. Duehay's letter defended the present level of funding as essential to insure decent housing for low and moderate-income Cambridge residents.

Duehay also stated in his letter that Cambridge has used a large part of its CDB grant to rehabilitate existing housing owned by low-income people. Under the proposed levels of funding, the letter said, Cambridge would have difficulty even maintaining its existing public housing.

Cambridge would also be hurt by rollbacks in the popular Urban Development Action Grant (UDAG) program, added Duehay in the letter. The program, which provides funding for public improvements, is valuable for its job development potential, the letter said.