The high-profile Conservative chair of the Commons education select committee has waded into the row over the Government's sudden introduction of the English Baccalaureate (EBac).
Graham Stuart, who is heading an inquiry into the new league table measure, said he fears it will leave "little room" for subjects like music, while provision for less able pupils would be "dismantled".
Despite his committee still taking evidence on the subject, Mr Stuart aired his concerns on the controversial performance measure in advance of publication of the inquiry's findings, in an article published last week.
His comments echo many of those made by headteachers when the EBac was unveiled last autumn. Mr Stuart warned that the qualification - which requires at least grade C GCSEs or IGCSEs in English, two sciences, maths, history or geography and a language - "leaves little room for other courses such as drama, economics, music, ICT or vocational courses such as young apprenticeships".
The MP also made comments along the same lines in Achieve magazine, published by Cambridge Assessment exam board, which put him at odds with his own Government's policy and with the findings of the Wolf report on vocational education, which it commissioned.
The Department for Education says the EBac has been designed to benefit and meet the needs of all pupils. But Mr Stuart believes that the less able could suffer because of it.
"It would be a shame if effective provision for lower-performing pupils was dismantled because it didn't fit with the EBac," he writes.
The MP adds. "After all, many schools have used vocational qualifications to re-engage disaffected pupils."
But the Wolf report rubbished "claims" that vocational qualifications were more motivating for pupils, leading them to achieve higher grades in other subjects.
It said: "Neither the existing research literature, nor analyses carried out for the review by academics and DfE analysts, found any indication that KS4 students (whether generally, or more specifically those `at risk of disengagement') made substantial improvements in their general attainment as a result of taking more vocational courses."
Mr Stuart goes on to repeat the criticisms that schools in his East Yorkshire constituency have made of Government policy on the EBac.
"They say that the Government promised to trust teachers and support heads in deciding how best to meet the needs of their students," he writes. "My local heads think the EBac does the exact opposite."
Mr Stuart says he understands ministers' desire for rigour through the EBac but wants them to "remain open minded on the issue".
He concludes that he wants to ensure "that the benefits of the EBac are not outweighed by the costs".
A DfE spokesman said: "The EBac is not the be-all and end-all. The core subjects has (sic) been kept small deliberately to allow the opportunity for wider study - there are valuable and rigorous academic and non- academic qualifications, not in the EBac, that pupils should be free to take."
Exam board chief - Criminal jibe
Mr Stuart's comment's echo those of Mark Dawe, the chief executive of the OCR exam board, speaking to The TES earlier this month.
He said the EBac league table measure could "massively distort the behaviour of schools", with potentially "criminal" consequences.
"If we just channel (pupils) down the GCSE route, a whole load of learners would be disengaged," Mr Dawe said.
"You see it time and time again, when you try to push learners on to a particular route and it's wrong for them, they have disengaged and, at 14, that's it for them.
"It would be disastrous if that was the approach that was taken."