The development of Mercedes' dominant engine should be frozen until its rivals have caught up, according to Toro Rosso boss Franz Tost.
Mercedes has dominated the V6 turbo era since it started in 2014, winning three consecutive drivers' and constructors' championships. In those three years Ferrari, Renault and Honda (who joined the grid in 2015) were hampered by the restrictive engine token system which limited development, though that has been scrapped for the upcoming season.
Last year teams agreed to engine regulation tweaks aimed at addressing four areas of concern with the V6 turbos, which includes an attempt to converge engine performance to prevent another season dominated by one team. The FIA plans to measure the gap between engines at the start of the 2017 campaign, which also sees massive regulation changes on the aerodynamic side, to see if further rule changes are needed to bring performance levels closer.
Though Mercedes' rivals have cut the gap in recent years and the new rules are better suited to development, Tost believes Mercedes' advantage needs to be dealt with in a different way.
"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."
Though the tweaks to the engine will be staggered over 2017 and 2018 to progressively cut costs, Tost believes Formula One still has to address the amount of money teams are spending on a yearly basis. He believes a cost cap -- something the smaller teams have been calling for in recent seasons -- is the only way F1 can control the teams' finances.
"We have to come down with costs. 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."