The 39-year-old Swede won the DTM title for Audi in 2004 and '07, and then added the World RX crown with his own EKS team in 2016.

The future of his rallycross programme - which attracted full Audi works backing last year - had been uncertain over the winter, as he put his existing Audi S1 Supercars up for sale, and team-mates Toomas Heikkinen and Reinis Nitiss both parted company with EKS.

But on Monday Ekstrom announced that after five seasons of dovetailing his DTM career with increasing rallycross commitments he would concentrate entirely on RX this year.

Ekstrom expects Audi to increase its backing of his rallycross effort, and said the team was preparing new cars for 2018.

"Pretty early last year I decided to do one championship for 2018," Ekstrom explained.

"Then I was in the [DTM] title fight, it didn't really play to my wishes but second is still OK, and when I left Hockenheim I said I would definitely come back. That was my spontaneous decision - I would continue to do DTM.

"Then as weeks and months continued I started to think about what I really would like to do because I know I don't have 20 years left as a driver.

"I had a lot of discussions with family, friend and [Audi Sport boss] Dieter Gass, and out of this discussions more and more it came that I think I would like to say goodbye to DTM and do just rallycross and focus on this.

"It's probably the most difficult decision of my professional life, because my heart has been beating for DTM for so many years."

Ekstrom emphasised that a desire to spend more time with his family was the main factor rather than any decline in his interest in the DTM, which faces an uncertain future with Mercedes poised to depart for Formula E after this season.

"I didn't feel for one second that I wanted to stop [racing], but I also felt that I would like to spend more time at home and with my family," he said.