Mercedes chief Toto Wolff believes the manner in which the top teams in Formula One are spending money is not a viable long-term strategy.
Speaking to Autosport ahead of discussions about a possible cost cap in 2015, Wolff admitted that the excessive spending at the front end of the grid is a threat to the future of the sport.
"Probably the highest spending teams spend three or four times the money of those other teams. Is that sustainable and healthy? No," the Mercedes chief told Autosport.
"Efficiency is what is being asked from our mother company, but the gaps, if you take the highest spending team compared to the midfield teams like Force India, Williams and Sauber, are still huge.
"I think the introduction of the F1 Strategic Group is going to be a first step of managing the situation.
"And we have heard that Bernie [Ecclestone] has started to emphasise on the fact that it is not a sustainable model.
"So I see that major stakeholders are pushing towards a more sustainable F1, a more balanced F1, in terms of financial resources."
Earlier, Caterham Team Principal Cyril Abiteboul suggested that F1 runs the risk of becoming an 'arms race' between manufacturers, particularly with the return of Honda in 2015.
"They need to justify the level of spending that is currently being put into it - and that obligation to win is going to create a massive arms race between them," Abiteboul said.
"That is a big danger for Formula 1 - that it will be those four and the rest of us behind."
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