Massachusetts Treasurer Steve Grossman Tuesday proposed that state pension fund executive director Michael Trotsky take on the additional role of investment chief.

The $50 billion retirement fund for state workers, formally known as the Pension Reserves Investment Management Board, or PRIM, has had a number of key vacancies on its investment staff. The most gaping of those has been the investment chief’s role, following the June departure of Stanley P. Mavromates Jr.

Trotsky, a former hedge fund executive who has overseen the state fund for two years, has been acting investment chief since then.

Grossman proposed that Trotsky would earn $50,000 more than his current $245,000 pay, plus bonus. The pension board could realize the rest in savings or use it to hire other staff or give raises, he said. The board has long faced difficulty retaining investment talent because people can earn far more in the private-investment sector in Boston.

The investment committee agreed to make the recommendation to the full board, although several members expressed concern that the combining of two major posts could result in the loss of important oversight.

Mavromates, the fund’s longtime investment chief, left in June. He joined the consulting firm Mercer, as chief investment office for the Americas.

At that time, Trotsky warned that the vacancies had created an “unacceptable level of risk,” with other workers having to pitch in to do the work of colleagues who had left.

PRIM has received complaints from municipalities that entrust their investments to the state. Those complaints have expressed concern about the job vacancies.