Two banks in Harvard Square are planning to follow the lead of the Harvard Trust Company and expand, it was learned yesterday.

The Cambridge Savings Bank has notified the tenants in offices on the top three floors in their building that they plan to use this space, possibly next year. If such a move is made, approximately 30 dentists, lawyers, chiropodists, and real estate and insurance agents will be without offices.

This expansion program has raised the possibility of erecting a new office building to obsorb these people, Bradlee F. Clarke, president of the Harvard Square Business Men's Association, said yesterday. A proposed site for the new building is the corner of Brattle and Story streets, which is now occupied by an old apartment house, Clarke added.

Another bank, the Reliance Cooperative Bank on Dunster St., is also considering an expansion, a member of the board reported yesterday. The upper floors of the building are now apartments which would be turned into offices if the plan is approved, Clarke explained. New apartments "might or might not be built" to house those people, he added.

One Harvard Square merchant complained that bank expansion was making it extremely difficult for people to get office space in the area. "The banks were nourished by the people whom they are now evicting," he said.

The expansion of Harvard Trust and the Coop may be a good thing for the Square, an official of the Cambridge Civic Association said, because fewer business establishments might mean less commercial traffic in the area.