Spiralling budgets in F1’s traditional feeder categories have forced an increasing number of young drivers to abandon their Grand Prix ambitions and turn towards alternatives such as sportscars and DTM.

Even those who have had an opportunity to prove their talent have found it a struggle to break into the highest level, with dominant GP2 champion Vandoorne facing another year in the F1 reserve driver role - and a possible switch to the Japan-based Super Formula series next season.

Coulthard said that this trend poses a major issue for F1, which he thinks could find itself increasingly starved of the best young talent in years to come.

“There seems to be a fundamental problem with the ladder into F1,” he told Motorsport.com. “We are losing more of the champions of lower formulae.

“In the past F3000 or even F3 champions moved on to F1, but now they don’t make it any more.

“Obviously, there are now less cars on the grid in F1 so there are less opportunities, and somebody has to pay in the end.

“That makes it difficult for most young drivers, and I’ve never seen such depth in F3 in my whole life,” added the Scotsman, referring to this year’s 33-strong European F3 field.

One driver still in with a chance of making his Grand Prix debut next year is DTM champion Pascal Wehrlein, who is remains in contention to land a seat with the tail-end Manor squad.

Coulthard, who competed in DTM from 2010-12, singled out the German tin-top series as one category that still offers a passage to F1 for young talents.

“DTM seems to be the one formula that either drivers come back to from Formula 1 or come up from DTM to Formula 1,” he said.

“You’d expect single-seaters to be the more obvious way, but it doesn’t have to be that way.”

Interview by Stefan Ziegler