The number of complaints about secondary schools' admissions arrangements has more than doubled over the last year.
New figures reveal the numbers of referrals received by the Office of the Schools Adjudicator (OSA) in 2010 was 258 - a 145 per cent increase on the previous year.
An OSA spokeswoman said the increase was due to the rise in the number of schools acting as their own admissions authorities, which now stands at more than 5,000, as well as an increase in multiple challenges to the same school or local authority being lodged.
Admissions campaigners have warned that the number of objections received by the OSA could rocket even further due to the Government's plans to abolish local authorities' admissions forums.
Under the current admissions code - due to be replaced this year - the forums offer a first port of call for parents, schools and councils to discuss problems with existing arrangements. The matter is only passed to the OSA if schools fail to heed the forum's advice, and the forums also submit annual reports to the OSA.
But the schools white paper, published last November, said the Government intends to end the "bureaucratic requirements", with the OSA instead to review complaints about all schools.
Faith schools have come in for frequent criticism of their admissions policies, but the new figures show the number of objections to them has dropped by more than half since 2008.
In contrast, the number of objections to county-wide admissions arrangements has more than trebled, from 16 in 2009 to 58 in 2010.
Margaret Tulloch, secretary of fair-admissions campaign group Comprehensive Future, warned that the OSA's workload would continue to increase without forums to resolve local issues.
She attributed the rise in objections to increased awareness of the admissions system, and criticised the Education Bill's proposal to reduce the adjudicator's power by stripping him of some powers to scrutinise schools' codes.
"This is another reason why we don't want his powers to be reduced," Ms Tulloch said.
"Admissions forums are local bodies which allow admissions to be discussed and comments to be made. Parents can make representations about issues concerning them and make a difference. This will really make it harder for them to challenge admissions arrangements.
"The bill will also restrict the adjudicator's power to just deal with specific complaints. He has the power to change arrangements if schools don't comply with the code. That power would be taken away. It would mean he can recommend changes, but can't change it himself," she added.
The figures were released after a surprise announcement last week from the Department for Education (DfE) that adjudicator Ian Craig is leaving his role sooner than expected.
His contract was due to end in April 2012, but he will now leave his post in October after giving his final annual report. He took up the post in April 2009.
The DfE announcement said Dr Craig, who has publicly warned the Government not to "water down" the code by over-simplifying it, and education secretary Michael Gove agreed to bring his departure forward to allow his successor to "get up to speed".
Dr Craig thanked Mr Gove for his "considerable support", adding: "With a new admissions process coming into force in 2012, I feel the time is right for a new chief adjudicator to take on the role."