Plans for a race on a 5.1km circuit taking in sights including Buckingham Palace, Big Ben and Trafalgar Square were unveiled last month.
The event was seen by many as nothing more than a publicity stunt for sponsors Santander, but Formula One supremo Ecclestone insists he is pressing ahead with the idea of a London Grand Prix in some form.
"We are getting on with it," he told the Guardian. "It is no joke, 100% completely no joke."
Ecclestone also suggested the sport could help to fund the race should it happen.
"With the way things are, maybe we would front it and put the money up for it," he said.
"If we got the okay and everything was fine, I think we could do that."