Red Bull team boss Christian Horner reckons his drivers could have challenged for championship titles during the 2018 Formula 1 season with an extra 40kW of power.

Max Verstappen and Daniel Ricciardo each won two races in 2018 while Verstappen ended the season by scoring the most amount of points by any driver apart from world champion Lewis Hamilton.

Red Bull will end its long-term partnership with Renault in favour of a switch to Honda power next season in its bid to challenge for world championships for the first time since 2013.

Top 10 of F1 2018 Moments

“It’s always easy to say ifs, buts and maybes. If there would have been another 40kW in the back of the car then the season could have looked quite different,” Horner said.

“Hats off to everyone at Milton Keynes to arguably producing one of our best ever chassis.

“If you look at the other users with the same engine [Renault and McLaren], there’s a world of difference.”

Asked what would happen if 2019 started with Mercedes, Ferrari, Honda and Renault all at the same level of performance as at the end of 2018, Horner replied: “I think we will certainly be a lot closer.

“What we see and hear in the pipeline as well. Pieces of paper are one thing, the stopwatch ultimately never lies.”

While Honda has made impressive performance gains with Red Bull’s sister squad Toro Rosso, reliability has been a concern at times with Pierre Gasly and Brendon Hartley both being hit with a number of grid penalties throughout the year, though some had been down to Honda’s aggressive development push in the latter stages of the campaign.

Red Bull also suffered a number of reliability issues with Renault throughout the season and Horner suggested Honda did not need to have perfect reliability in 2019.

“Reliability isn’t something we’ve had,” Horner admitted.

“We’ve had 11 or 12 retirements this year - that’s our biggest achilles heel. If we can achieve the power and reliability.

“Lewis had one DNF this year, likewise with Sebastian. That’s the rate we have to be aiming to achieve.”