The head of England’s exams regulator has called for ministers to drop all targets for schools related to the number of grade-C GCSE passes.

Isabel Nisbet, Ofqual chief executive, also dubbed the current school league tables “simplistic” and said they could lead to people drawing “false conclusions”.

The grade-C GCSE threshold has been a crucial goal for secondary schools ever since league tables were first compiled and the Government began to set targets based on exam results. But critics complain it has led to too much emphasis being placed on borderline CD pupils.

At a Cambridge Assessment conference last week, Ms Nisbet said: “I would get rid of the targets related to the number of passes at grade C at GCSE.” Her comments follow ministers’ call for a “real debate” about what 16-year-olds should be expected to achieve and how it should be measured.

A white paper expected before Christmas will unveil a complete overhaul of the league table and assessment system.

Brian Lightman, Association of School and College Leaders general secretary, said he agreed with Ms Nisbet.

“The problem with these targets is they focus entirely on the C grade rather than what the student could achieve,” he said.

Ms Nisbet, who is leaving Ofqual in March, also suggested there are flaws with league tables.

“The question is, is it simplistic to measure a very small number of indicators, sometimes drawing false conclusions? I think the answer is it probably is.”

But she said the solution was not to restrict the information available to parents about schools, but to give them more. There needed to be an “opening out rather than a closing in”.

Ms Nisbet said people were “very sophisticated” and understood that there were different schools, serving pupils with differing backgrounds.

Last month, Education Secretary Michael Gove used similar reasoning when said he was “determined” to publish all exam data held by Government so that parents could use computer applications to create their own bespoke league tables.

But the Ofqual chief executive’s call for the end of targets relating to grade-C GCSEs may be a less good fit with Mr Gove’s plans.

The Education Secretary has proposeded the creation of an “English Baccalaureate”. It would demand pupils to achieve a balanced mix of five GCSEs, including “English, maths, a science, a modern or ancient language and a humanity like history or geography, art or music”.

But there would also be an expectation of “good passes” he said, implying a continued emphasis on the importance of grade-C GCSEs.

Ms Nisbet also said there were “lessons to be learned” from the controversial Diploma, introduced by the last Labour government.

She said it was “too complicated”, that there was an issue about hurdles such as functional skills tests that pupils had to clear to gain the qualification.

She also said that the administration of the Diploma was “quite burdensome”.

• Original headline: Ofqual chief lays it on the line: C-grade GCSE targets should go