Christian Horner has accused his rivals of under-delivering this season which has played a part in Red Bull’s dominant start to the F1 campaign.

In the Miami Grand Prix, the team scored its fourth one-two from the opening five races as Max Verstappen led home team-mate Sergio Perez despite starting from ninth on the grid compared to the Mexican’s pole position.

Two-time F1 champion Verstappen now has a 14-point lead over Perez who, in turn, is 30 points clear of Aston Martin driver Fernando Alonso.

It is in the constructors’ championship, however, where Red Bull’s dominance – and its best start to a season in its history – is fully illustrated as it is 122 points clear of second-placed Aston Martin.

If you combine Aston’s 102-point haul with the 96 from third-placed Mercedes, it still falls 26 points short of Red Bull’s 224-point tally.

Asked by Speedcafe whether he was anticipating his rivals to pose a challenge at any stage this season, Horner replied: “You can never write anybody off.

“It’s been the best start that we’ve had, and we feel we’ve made a good step from RB18 into 19. It’s the kind of step you would expect.

“So I think it’s more that…it feels like others have lost ground. I’m sure they’re working hard to address that. Big gains could come quite quickly.”

Horner waiting to see rivals’ upgrades

Horner was at least expecting Mercedes and Ferrari, in particular, to have progressed their cars from last season – the first of the new aerodynamic regulations – into year two.

“It’s surprised us that others have perhaps under-delivered compared to where they were last year,” added Horner.

“But no doubt they will be looking to address that. I’m sure starting (at the next race) in Imola we’re going to see big updates starting to come through.”

Ferrari introduced a new floor for the race in Miami, and further updates are planned for the Emilia Romagna Grand Prix in which Mercedes will unveil its first major upgrade as it attempts to address its W14 that team principal Toto Wolff has called “a nasty piece of work”.

Suggested to Horner that if the present gap is maintained after Imola, this season is all over bar the shouting, he said:

“Until mathematically when things are done, which is still a long, long way away…” he said.

“We’ve got a great car, a great team, two great drivers, but there’s still a long way to go.

“Let’s reserve judgment until after we see what they (Mercedes and Ferrari) turn up with at Imola and Barcelona.”