Mercedes have had the most powerful 1.6 V6 Hybrid engine since it's introduction in 2014, leaving Reanult, Ferrari and Honda to play catch up. The FIA confirmed last year that some minor parts of the engine development would be frozen in 2017 such as minimum MGU-K and MGU-H weights.
However Tost believes that the FIA need to go a step further and ban Mercedes from developing their engine altogether.
"I hope that earlier or later there will be a power unit parity because this is not the case currently," Tost told Autosport. "We need Red Bull Mercedes and Ferrari fighting for the championship at least. If the power unit parity is not coming then the FIA should come up with a regulation to freeze it.
"I would freeze the power unit from Mercedes, the others should catch up and then they freeze all of them. I would leave the development of the battery free because the battery is something for the future and it is also something important for the manufacturers."
Price caps have been pondered for a while now, with F1's new owners Liberty Media interested in introducing them. Tost has backed the motive.
"We have to come down with costs," he said. "We have discussed this for years now but nothing happens. I would come in with a cost cap. People say it's not controllable but that's nonsense. At Toro Rosso we have a history about every screw and we can tell you where it's coming from and how much it costs."
Bahrain International Circuit - Winter testing