Sir Jackie Stewart believes the British Racing Drivers' Club would have gone bankrupt if they had continued to stage the British GP.
The BRDC, who own Silverstone, were yesterday struck by a bombshell when F1 supremo Bernie Ecclestone announced Donington Park would host the race from 2010.
Although they recently confirmed plans for a new £30million paddock and pit complex, Ecclestone had run out of patience with the BRDC.
Stewart, a former BRDC president, feels Ecclestone's demands for a new contract of £11million per race, with a small percentage rise per annum, would have crippled the organisation of which he is still a member.
"I am disappointed Silverstone is losing the British Grand Prix," Stewart said.
"But, quite frankly, it is very difficult for a private members' club to try and continue to afford the kind of monies needed to retain the race in this country.
"Almost every other country in the world that hosts a grand prix, if not every one, has government support.
"I don't think there is the opportunity for any promoter, given the present cost of Formula One, to make ends meet.
"For the BRDC to continually lose money, just to keep the British Grand Prix, is not correct.
"Eventually it would have bankrupt the BRDC."
Shunning Silverstone's plans, Ecclestone has instead agreed a 10-year deal with Donington, which will require its own £100million revamp to bring it up to Formula One standards.
That is due to take place over five years, with the initial two of those spent getting the track in shape in time to host their debut British GP.
Three-times F1 World Champion Stewart has questioned how Donington can make a profit on such a large-scale redevelopment, even though a private investor is due to finance the plans.
There are suggestions that is Ecclestone himself, although the 77-year-old denied this when pointedly asked yesterday.
Assessing Donington's financial viability, Stewart added: "I wish Donington well with it, but I know it's not possible for them to financially justify it.
"The money they're going to have to spend, to enlarge the circuit, put the facilities in that are required, will be considerable.
"Most of those facilities are already here at Silverstone, and it would take maybe £30million, but it's going to cost Donington more than double that.
"It's then not financially viable, so how can we seriously think it's correct something not financially viable can be affordable?
"It's unfortunate timing as well, to announce it at the British Grand Prix. It should have been announced in the middle of next week."