BOSTON — Ruth Ayres, evp/chief marketing officer of Hill, Holliday, Connors, Cosmopulos for about 18 months, on Friday resigned from the Boston-based Interpublic Group shop, effective Dec. 15. An agency representative said Ayres will not immediately be replaced. Gayle Nyre, an svp, is now the top-ranking new-business staffer in Hill, Holliday’s Boston headquar ters; Elizabeth DeMaso and Jenifer Wallrapp head new business in the shop’s New York and San Francisco offices, respectively. Sources said Ayres was stymied by the shop’s lack of new-business success , especially in the Boston office, where the only sizeable win in 2001 was the $10-12 million LoJack account, added just two weeks ago. Ayres strongly refuted assertions that she was asked to leave, saying she resigned to spend more time with her family in New York. She is currently consulting on marketing issues for an undisclosed toy manufacturer and is not seeking a new agency post, she added. Under Ayres, Hill, Holliday did add some $100 million in overall new billings in this year. However, Hill, Holliday also estimates 2001 revenue and billings nationwide fell nearly 15% each to $125 million and $835 million, respectively. Ayres joined Hill, Holliday from TBWA Worldwide in mid-2000.