Up to one in four school governor positions is vacant in some rural and deprived areas of England, says a group which matches schools with governors.
Governors for Schools says one in 10 of the 300,000 governor posts across the country is unfilled.
The charity says the figures on governor vacancies include posts coming to the end of their term of office as well as resignations.
It drew its estimates from its work with schools and local authorities.
The figures come at a time when pressure on governors to hold schools to account for their performance has been growing.
'Badge of status'
Education Secretary Michael Gove has said he wants to reform school governance and said in a speech a year ago that governors were often "local worthies" who viewed their post as a "badge of status not of work".
Instead he wants to see people taking up the positions because they have a skill and for them to "concentrate on essentials such as leadership and standards, teaching and behaviour," he said
The education inspectorate, Ofsted, requires governors to hold head teachers and other senior staff to account.
Governors for Schools (SGOSS), which receives funding from the Department for Education, also carried out research on the public view of governors and their role.
A Populus survey for the charity of 1,781 people in Britain found nearly two-thirds did not realise it was school governors' responsibility to appoint a head teacher.
Three-quarters did not know governors were responsible for deciding a school's admission policy.
And 85% of respondents were not aware that signing off a school budget was the governing body's responsibility.
The ﬁndings led SGOSS to develop its "School Makers" interactive video campaign which aims to raise awareness and recruit volunteers to help support England's schools.
In the video, would-be governors must navigate a series of decisions they might face in the job, such as whether to sell part of the school playing field in order to finance improved IT facilities.
Chief executive of SGOSS Liz McSheehy said: "We know that a full and diverse governing body is a source of enormous strength to a school.
"If people feel they have skills to offer and care about making a difference in their local community, we want to hear from them."
A Department for Education spokesman said: "School governors play an incredibly important role in setting the direction of a school, supporting and challenging the head teacher, and ensuring money is well spent.
"We are working with organisations including the CBI, the Education and Employers Taskforce and SGOSS to encourage more employers to support their staff to volunteer. "