The presenters made the quip earlier this month while hosting the ITV jungle show.
They apparently joked about suffering from PTSD (post-traumatic stress disorder) – which the NHS says is “an anxiety disorder caused by very stressful, frightening or distressing events” – when they heard their 1994 song Let's Get Ready To Rhumble.
PTSD UK weighed in, penning an open letter to ITV saying the condition was “not funny” and “not a subject to take lightly”.
Price – who previously revealed that she had been diagnosed with the disorder – then shared a screengrab of part of the letter on Instagram.
The star, who was an I'm A Celebrity camper herself in 2004, added a string of clapping emojis.
In the letter, PTSD UK said to ITV: "We’re writing to you with a heavy heart today to address the comment made in episode eight of the current I‘m A Celebrity season surrounding PTSD.
"To be specific, we’d like to highlight our issue with the comment made by Ant McPartlin shouting ‘PTSD’ and Declan Donnelly exclaiming ‘Flashbacks’ whilst their song Let’s Get Ready To Rhumble was played (insinuating that they were traumatised by hearing their old hit).
"There is little doubt that this comment was made in jest, but PTSD is not funny, and it’s not a subject to take lightly. It’s a serious condition.”
It said PTSD is a condition which some people get after experiencing a trauma and that using it as a punchline in a joke “not only further stigmatises the reality of the condition, but it also incorrectly and unhelpfully desensitises people to the debilitating symptoms that can lead to family problems, unemployment, physical health issues, self-harm, homelessness, alcohol and drug addiction, and ultimately suicide”.
It went on: “Jokes like this, using PTSD as part of the gag is only one in a long line of examples where people are using PTSD in a really disrespectful way – but feel that as the leaders of the mental health campaign Britain Get Talking you should be setting an example and so feel that ITV has a duty of care to its viewers which includes comments like this which are not only unnecessary, but can also be incredibly damaging to those affected by post traumatic stress disorder.
“We appreciate the duo’s script is likely written by a third party, so are not making assumptions, or directing this at any particular people, we simply ask that you try to do better.”
Price has previously shared that she was diagnosed with PTSD after being raped at gunpoint in South Africa.
Yahoo has contacted ITV for comment.
Watch: Katie Price reveals she was raped by carjackers