The board of the American Psychological Association plans to recommend a tough ethics policy that would prohibit psychologists from involvement in all national security interrogations, potentially creating a new obstacle to the Obama administration’s efforts to detain and interrogate terrorism suspects outside of the traditional criminal justice system.

The board of the of the A.P.A., the nation’s largest professional organization for psychologists, is expected to recommend that members approve the ban at its annual meeting in Toronto next week, according to two members, Nadine Kaslow and Susan H. McDaniel, the group’s president-elect. The board’s proposal would make it a violation of the association’s ethical policies for psychologists to play a role in national security interrogations involving any military or intelligence personnel, even the noncoercive interrogations now conducted by the Obama administration. The board’s proposal must be voted on and approved by the members’ council to become a policy.

The board’s recommendation is a response to a report from earlier this month after an independent investigation into the involvement of prominent psychologists and association officials in the harsh interrogation programs operated by the C.I.A. and the Defense Department during the Bush administration.