Although TV audiences have dropped in Italy, the Italian Grand Prix is still one of the most well-attended races on the calendar

Formula 1's race organisers have expressed concerns over the future of the sport and demanded a more open approach from its owners.

The F1 Promoters' Association (FOPA), which represents 16 of the 21 races on the calendar, says it wants "a more collaborative approach from F1".

The FOPA discussed its concerns with F1 at a meeting in London on Tuesday.

Stuart Pringle, chairman of FOPA, said: "There is every indication the message has been received."

Pringle is managing director of British Grand Prix venue Silverstone.

The circuits are worried about the loss of free-to-air television coverage, a lack of clarity over rules and the methods F1 is using to attract new races.

And they feel that their voice has been ignored so far by the owners of F1, the US group Liberty Media, which took over the sport in January 2017.

Pringle added: "We were frustrated that we felt we had no option but to take this sort of action. But actually we have had a very positive day.

"We believe our concerns will be looked at and we as a group of promoters do recognise that ultimately we are all striving for the same thing - a healthy sport. We want to work in a meaningful way to achieve that so we will work collaboratively with them going forward."

Pringle had earlier described Liberty's approach as "disjointed" and said the circuits had "great concerns about the future health of the sport under the people who run it now".

The circuits' intervention comes at a delicate time for F1, with the contracts of five major races all up for renewal at the end of this season. Britain, Italy, Spain, Germany and Mexico are all out of contract after this year.

All want to continue but say they cannot do so under the financial terms on offer from F1.

Race-hosting fees are the single biggest source of revenue for F1, so the circuits hold a strong hand in discussions.

F1 declined to comment on the specific issues raised by the circuits.

In July, John Grant, chairman of the British Racing Drivers' Club, warned that "as things stand, 2019 could be the last British GP at Silverstone"

What are F1's plans?

Liberty is determined to make major changes to the way F1 is run. But talks on their plans to introduce a budget cap, reorganise revenue distribution to the teams and change the technical rules to make the racing closer have progressed slowly.

F1 has already had to abandon a plan to change the engines significantly, but it insists negotiations are moving forward.

There has been no public confirmation of any agreements as to the shape of the sport after 2020, when the teams' current contracts expire.

Sources close to F1 say that there is general agreement on the principle of a budget gap and revenue redistribution but nothing concrete has been agreed.

The latest plan is for a sliding scale of budget restriction, starting at around $175m in 2021, and reducing to about $135m in 2023. But the exact numbers are yet to be finalised and a number of areas of spend will not be included - such as engines, marketing and the salaries of the most expensive employees, including drivers.

What are the circuits' concerns?

The circuits say it is a risk for them to be asked to plan long-term contracts with a partner without knowing the direction in which the product is heading.

They have been concerned by what they believe was Liberty's willingness to give an advantageous deal to Miami, which insiders claim was effectively offered a race for free because F1 was so keen to secure an event in the Florida city. Efforts to finalise a deal have so far foundered.

A statement from the circuits said: "There is a lack of clarity on new initiatives in F1 and a lack of engagement with promoters on their implementation.

"New races should not be introduced to the detriment of existing events although the association is encouraged by the alternative business models being offered to prospective venues."

The circuits are also concerned that the migration of TV coverage away from mass-market outlets towards either pay television or direct to consumer through F1's own outlets will inevitably restrict the sport's appeal.

The statement said: "It is not in the long-term interest of the sport that fans lose free access to content and broadcasting."

The UK is the latest market to effectively lose live coverage of races in 2019.

A new contract, negotiated by former F1 boss Bernie Ecclestone before Liberty took over, kicks in which sees live coverage of all races on Sky this year. Only the British Grand Prix will be live on free-to-air, on Channel 4, which also has highlights of the other 20 races.

The circuits believe that moving from free-to-air will inevitably restrict F1's reach to casual viewers, restricting it only to hardcore fans, which has an immediate effect in cutting the audience but also threatens the sport's appeal in the long term.

This is of particular concern to Silverstone, which saw attendance drop for its MotoGP race after it switched from free-to-air TV to pay-to-view and is concerned the same thing could happen with F1, further affecting its ability to afford to host the British Grand Prix.

The UK TV switch follows a similar move in Italy last year.

F1 points out that its overall TV audience has grown in the two years since Liberty took over, for the first time in a decade. The total audience in 2017 was 1.755 billion and 1.758 billion in 2018.

However, live race audiences dropped slightly from 2017 to 2018, the total brought down by a decline in Italy, without which numbers would have gone up year on year.

The races represented by FOPA are: Australia, Austria, Azerbaijan, Belgium, Brazil, Canada, China, France, Germany, Hungary, Italy, Mexico, Singapore, Spain, Britain and the USA.