Sir Jackie, president of the British Racing Drivers Club, made it clear that money is the main resource required to bring the track up to scratch.
"The British government have been very receptive to the fact that we would like them to match the private funding we have," the 62-year-old told BBC Radio Four.
"That is being shared by a company called FOM and Octagon, and the BRDC for roughly £40m."
Stewart confirmed a sum of £40m would need to come from the government over a period of three of four years
He also responded to the criticisms of the track as it is now.
"Silverstone is far from being the worst track in the world - I think it's in the top six."
"It needs a lot of improvement.
"If we do all the work that is required to make it a centre of excellence there is no doubt we can keep the British GP in this country under correct circumstances."
"Octagon who now lease the track have made a tremendous number of improvements for this year for car parking and preparing for the potential for rain."