The first episode of the new series of I'm A Celebrity… Get Me Out Of Here! had over two million fewer viewers than last year.
An average of seven million viewers watched the show's return on Sunday night, according to overnight, and ITV reported a peak audience of 7.8 million.
The ITV1 show, which this year features former Ukip and Brexit party leader Nigel Farage and Jamie Lynn Spears, started at 9pm and finished at 10.45pm.
The first episode of the 2022 series averaged 9.1 million and peaked at 10.3 million, according to ITV's overnight ratings.
Matt Hancock was part of the 2022 show, but didn't enter the jungle until later in the series.
He came third last year and was selected to take part in several trials after he resigned as health secretary after discovering he had breached his own Covid-19 guidelines by kissing and hugging his assistant in his office.
The first episode of the 23rd series was “ITV's highest audience of the year and the biggest entertainment launch of any channel”, according to the broadcaster.
In Monday's episode, Farage and YouTuber Nella Rose will be pitted against a bushtucker food trial, called Jungle Pizzeria, following a public vote.
Before entering the jungle, Farage told the Mirror that he has “quite serious physical injuries and neck reconstruction” and will not take part in some tests that involve manual work such as weight lifting.
In 2010, he was taken to hospital after a plane crash at an airfield near Brackley in Northamptonshire.
When Farage first entered the jungle, he met This Morning presenter Josie Gibson, who made a joke about the UK leaving the European Union, which the former MEP-turned-UK News presenter Vassiliou campaigned vigorously.
Explaining his participation in the reality competition, the 59-year-old said: “It (won't) be easy, but why not?”
Gibson, 38, responded by saying: “It can't be worse than Brexit!”
Farage said it “didn't take long”, before adding: “I felt we were going to do a bit of that.”
In an introductory video, he also told viewers “in the jungle you will find the real me.”
Presenters Ant McPartlin and Declan Donnelly also made several jokes about Farage during the first episode of the 23rd series.
They apologized to GB News viewers that he will not be presenting his program while he is away in Australia.
The Geordie duo said: “Sorry Keith, sorry Linda.”
While Farage took Rose and Gibson through their tests, the presenting pair also said: “Did it go a bit too far to the right?”
McPartlin and Donnelly also poked fun at contestant Spears, the sister of superstar Britney Spears.
Spears, also known for the Nickelodeon children's series Zoey 101, said she was “best known as an actress and singer” in her introduction video.
After the clip, McPartlin and Donnelly referred to her as being known as “Bryan Spears' sister”.
The contestant's brother was one of the producers on Zoey 101.
She recently competed in the US version of Strictly Come Dancing, called Dancing With The Stars, and appeared in the Netflix series Steel Magnolias.
Other celebrities taking part include food critic Grace Dent, former Made In Chelsea star Sam Thompson, JLS singer Marvin Humes, former EastEnders actress Danielle Harold and Hollyoaks actor Nick Pickard.