The head of the exam board regulator has rejected suggestions that paying markers more will increase standards.

School leaders have been complaining about a lack of confidence in the exam marking system, with the Headmasters' and Headmistresses' Conference (HMC) hearing earlier this week that 414,000 marks were challenged last year, with a "shocking" 77,450 GCSE and A-level grades being revised, representing a 42% increase on 2013.

Addressing the conference in St Andrews today, Ofqual chief executive Glenys Stacey said "much progress" has been made in improving certain areas of the system but it was found that a pay rise would make little difference.

"We know from extensive research that most markers don't do it for the money, much like I'm sure most of you did not choose a career in education for the money," she said.

"Instead, most teachers become markers to get close to exam board specifications and mark schemes. It is not clear to me that paying markers more will of its own deliver improvement, although of course we don't argue against this."

She pointed out that despite the volume of review requests to exam boards last year, more than four out of five were within the original marking tolerance and fewer than 1% of all grades awarded overall were altered.

Ms Stacey said that alternative marking systems have been tested, including single-blind and double-blind review, but none performed noticeably better than the current system.

Double marking could also cost as much as £10 million extra, she said.

On Tuesday, Chris King used his inaugural speech as HMC chairman to call for widescale and urgent reform to the system, which he described as not fit for purpose.

The head of Leicester Grammar School argued that a lack of full accountability by exam boards, an inadequate examiner workforce, and a "confusing and byzantine appeals process" were all contributing to the problem.

"We are facing a perfect storm, of both decreasing public confidence and increasing pressure in the system, as the greater emphasis on end of year exams creates even more work for examiners over the summer," he told delegates.

Ms Stacey, who is stepping down from her role at the end of the year, acknowledged Mr King's call for a larger marker workforce.

"We welcome all efforts on your part to encourage good teachers to play their part in marking and awarding," she said.

"Marker capacity and planning are being actively considered by exam boards and we will continue to engage with them to assure us of their ability to get the job done."