Sebastian Vettel is to leave Red Bull at the end of the current season and join Ferrari, the team has announced. The four-times world champion is to be replaced by the Russian driver Daniil Kyvat, who currently races for Red Bull's second team Toro Rosso.

Ferrari, in turn, are expected to part company with Fernando Alonso, who is likely to head for McLaren, although no deal has been announced. Vettel is understood to have told the team his intentions late on Friday night.

The Australian Daniel Ricciardo will move up to senior driver at Red Bull, with Kyvat slotting in as number two. Kyvat's move will leave a vacancy alongside Max Verstappen at Toro Rosso.

“This is not a decision against Red Bull it is for something else,” said Vettel, who is currently fifth in the world championship. “Red Bull did nothing wrong, we part as friends and it has nothing to do with the results even though they are not what we expected.

“I am loyal and I did not breach any contract. I am not running away from anything but there are times in life when you need something new and if there is an opportunity you have to grab it.”

His contract was due to run until 2015 but it is understood that he had an escape clause that he could exercise if he was below third in the championship after 30 September.

Red Bull team principal Christian Horner confirmed on Saturday morning that Vettel would be joining Ferrari.

“I obviously know him very well, we spend a lot of time together and you can see that he has had a bit on his mind recently,” he said. “Inevitably a decision like this you don’t take lightly but it was last night he sat down with us and informed us. So all I can do is wish him the very, very best for the future. He will still be close to our hearts at Red Bull, but on 1 January he will be a competitor.

“Obviously Ferrari have made him a very attractive offer,” he said.

Horner confirmed he had not opposed Vettel’s decision.

“If somebody’s heart is not there, it doesn’t matter what you have on a piece of paper,” he said. “It has to be right for both sides He has reached a stage in his career where he fancied a new challenge, that is his prerogative and, like in any relationship, if somebody’s heart is not in it then it is time to move on.

“I think the lure of Ferrari, a window has opened there with whatever is going on and he has decided the timing is right for him. That is his choice, and he has been around long enough to know his own mind.

“He doesn’t have a manager and doesn’t have people that surround him. He has made this decision and we respect that.”

Rumours had circulating the paddock on Friday that Vettel would be swapped for Alonso, but Horner denied that had been a realistic proposition.

Asked whether the idea had been entertained by the team, he said: “The reality is not really. Fernando is a wonderful driver, but our philosophy and policy is to invest inwardly, invest in youth and give youngsters a chance.”

He insisted the team would stick to its policy by promoting Kyvat, as it had done with Vettel and Ricciardo. Ricciardo also came up to Red Bull through Toro Rosso and has largely out-performed Vettel this season, with three wins.

“It has been our philosophy for several years now to back youth, to grow our own talent and that is exactly what we did with Sebastian,” he said. “There were question marks when we signed him, and question marks when we signed Daniel Ricciardo, but we have demonstrated that it works.

“Daniil is a very exciting talent and it is an exciting new dawn for Red Bull Racing. Does it leave us in the lurch? No. We have a fantastic driver in Daniel Ricciardo.

“When we took Seb he was a young driver - and we have demonstrated investing in young drivers works. I think it is the beginning of a new cycle, and things happen in cycles.

“Inevitably this was always going to happen at some point. It has happened today and it is time to look forward.”

Vettel drove his first race for BMW in 2007 but was signed by Toro Rosso in the middle of that season. He raced with them for two years before joining the senior squad in 2009. His career with them has been hugely successful, taking the team to the driver's and constructor's title every year between 2010 and 2013. In doing so he won 38 races for the team and took 44 pole positions.