Formula One's governing body the International Automobile Federation (FIA) has expressed its concern over the French Grand Prix's cancellation.
The 2009 French GP was cancelled after the French Motorsports Federation (FFSA) withdrew its financing.
"Up until today we have heard nothing and we are gravely concerned," said a FIA spokesman.
Magny-Cours was due to stage the race on 28 June 2009 but France will now not feature on next season's FIA calendar.
"The FIA secretary general has written to the president of the FFSA today to seek an urgent clarification of the situation of the French Grand Prix," added the FIA spokesman.
The FFSA confirmed that all those who had already booked tickets would be reimbursed and apologised for the inconvenience caused by the cancellation.
France has only once been absent - in 1955 - from the F1 calendar since the championship started in 1950.
The FFSA has a contract to run the French Grand Prix until 2011 but F1 boss Bernie Ecclestone has long wanted to move it to a track closer to Paris from 2010.
Next year's race had already been billed as the last at Magny-Cours, a circuit in the depths of rural France that has fallen out of favour with teams and sponsors.
Ecclestone had wanted to axe it but agreed to a reprieve and the circuit retained its slot on an 18-round calendar published last week.
That calendar was notable for the absence of the Canadian Grand Prix in Montreal, which had been on an earlier 19-race provisional list.
Poor accommodation facilities and difficult access were regarded as the main weaknesses of the Magny-Cours track.
Disneyland Paris is reportedly a favoured option for a future French Grand Prix, with plenty of hotel rooms and easy rail access from Paris and the rest of Europe.The FFSA said it was studying six "serious and worthwhile" projects, most of which involved a new track near the French capital.