Ant stepped down from TV commitments earlier this year, missing the previous Britain's Got Talent live shows.
Last month he confirmed he would not be back on TV for the rest of the year, not taking part in I'm A Celebrity Get Me Out Of Here.
It was previously announced in March that Ant was taking time off "for the foreseeable future" to seek treatment in rehab after pleading guilty to drink driving.
In a statement (released on August 9), Ant said: “My recovery is going very well and for that to continue having spoken to Dec and ITV, I have made the decision to take the rest of the year off. I’d like to thank both Dec and ITV for their continued support and I look forward to getting back to work in the new year.”
Dec added: “Whilst I am obviously sad at the thought of being without my best friend in Australia this year, I am proud of the work Ant has been doing privately and I am fully supportive of his decision. I’m looking forward to us both being reunited on screen in 2019.”
Holly Willoughby will co-host I'm A Celebrity with Dec while Saturday Night Takeaway will be rested next year and return in 2020.
No mention was made about Britain's Got Talent but it's fully expected Ant will be back for the next series.
Simon Cowell told The Sun newspaper: “That is what I always thought would happen, so I am happy to hear that. He is welcome back and we have missed him. But he has done the right thing by taking some time off, and he will come back fresh and will enjoy it.
“We didn’t speak while he was in rehab but we got messages through Dec – as we have always done – but I didn’t want to impose on his privacy.
"But we have always made it clear what our relationship is, we help each other. We are friends and he is welcome back anytime.”
I'm A Celebrity Get Me Out Of Here typically launches in November on ITV.
Britain's Got Talent begins filming in the new year.