Mercedes team boss Ross Brawn says a season finale on December 11 is "totally unacceptable" and revealed that the teams have told Bernie Ecclestone as much.
Ecclestone is considering moving the Indian Grand Prix back to December 11 in order to accommodate the return of the Bahrain Grand Prix to the calendar, having ruled out a December 4 date because of logistics.
Brawn, who had already said he was against a December 4 finale, believes Formula 1 teams will run into problems if the seasons continue to stretch.
And he said the December 11 date is "totally unacceptable."
"It is getting too much," said Brawn. "Our guys have been working since January, we don't have test teams anymore, so the same guys have been working since January and we are asking them to work into December and that means there is no time for a holiday before Christmas and that would mean getting straight back in to it in January.
"So personally I think it is unacceptable and we've told Bernie that and he knows our opinion. If we continue to take those sort of approaches then we will run into problems because our people cannot be expected to work in that environment and situation, so I think it is totally unacceptable."
Brawn said the teams needed to wait and see what happens with Bahrain before considering further action if they are forced to finish the season in December.
"The teams have opportunities to state their opinion. There are processes that we can get involved in to try and resolve it, so I think we should wait and see what happens with the question of the Bahrain.
"There is a WMSC meeting coming up, and that is what triggers the difficulty in the calendar. We need to see what happens there before we start to deal with this issue. We are not getting too excited about it, but the relevant people know our opinion."
The deadline for a decision on the Bahrain Grand Prix in on Friday.