Rishi Sunak faced humiliation as an expert picked by Downing Street to promote his maths plan criticised the policy.
Stephen Follows was asked to promote making students study maths until they are 18, but described the idea as “misguided and tone deaf”.
He had been asked by the PM’s office last Friday, days before the plan was announced on Monday, to become a “maths champion”.
The government planned to use Mr Follows as an example of someone in a “cool job you did not know you needed maths for”. But bungling officials neglected to ask if he actually supported Mr Sunak’s idea.
Mr Follows, a film data analyst, added that something did not “add up”, as he only studied maths until he was 16.
Downing Street had designed a graphic on Mr Follows, including a quote beneath a picture of him saying he “uses maths to empower filmmakers”. But the graphic has been ditched after he criticised the plan.
Mr Follows went on to launch a withering criticism of the “maths to 18” proposal, describing it as “grossly unfair”.
Writing in The Times, he said: “Last Friday, I was approached by the prime minister’s office to become a maths champion because today [Monday] our government is launching a policy obliging all students to study maths until the age of 18.
“Nobody thought to ask me whether I support this policy.
“I think their one-size-fits-all policy is misguided, tone deaf to the actual needs of students and may even be counterproductive.”
Mr Follows described how he uses maths to analyse the financial performance of films and study industry trends, but highlighted how he was driven to “self-educate” using online resources.
He went on to stress the importance of other skills including “emotional intelligence”, adding that to prioritise maths was “grossly unfair” on students.
“Forcing students to study maths until the age of 18 risks stifling the passions and interests of individual students, the very qualities that education should be cultivating,” Mr Follows said.
In a further twist, it emerged that Mr Follows was the only case study the government obtained for a planned social media campaign, despite him being opposed to the plan.
He said: “Instead of rushing to finish their homework just before the deadline, the policy makers at No 10 should apply themselves to understanding the diverse educational needs of students.”