The duo have fronted the show since its inception on ITV in 2002.
However they have confessed they were at first very dubious about the plans.
Writing in their autobiography Ooh! What a Lovely Pair: Our Story, the hosts confessed they weren't entirely convinced about the concept.
Dec wrote: "We listened intently to the idea, and shot each other a few sideways glances as they explained how eight celebrities would live together in a tiny camp in the middle of a rainforest for two weeks...
"After the meeting, I was slightly keener than Ant, although we were both interested. I just remember saying to him, 'We've got to do this because if it works, it'll be brilliant, and if someone else does it and it's a big hit, we'll be gutted."
Ant confessed: "But I just kept thinking, 'It sounds stupid - and that title's far too long'."
The Geordie pals went on to say that after the first series finished they weren't sure if the show would ever be back.
Dec explained: "The series finished and, after two weeks of solid night shifts, we were knackered. Although the show had developed into a hit, it had been a hard slog. We still felt we hadn't really got into our stride and when we left Australia, we weren't convinced we'd be doing the second series.
"We got home and got a sense of how much everybody had enjoyed that 'Z-list jungle show'. The public had watched in their millions, the press had changed their tune and so had we. We realised one another thing - doing more series would mean a month in Australia in the middle of the British winter every year."
Ant added: "We couldn't sign that contract fast enough."
I'm A Celebrity Get Me Out Of Here starts on ITV later this year.