Senior education officials allegedly instructed at least two teachers to inflate matric results, the Democratic Alliance said on Tuesday.
The party had been approached by two people who claimed that some matric marks were deliberately raised, said spokeswoman Desiree van der Walt in a statement.
They alleged that the increases were carried out on the instructions of education department officials.
One of the complainants, identified as a DA councillor and a former teacher, alleged that colleagues who were marking maths and science papers were told to increase the marks of weaker matric candidates.
The unnamed former teacher said colleagues had complained about having been told to increase the marks of weaker candidates, so that, for example 20 percent be boosted to 30, which was a pass.
The other complainant, a teacher involved in marking history papers, also alleged that the department instructed teachers that no pupil may get zero out of 30 for an essay.
The teacher further alleged that they were instructed that if pupils were able to produce just one fact, they had to be given nine out of 30 -- almost a pass. The marks in every one of these teacher's papers were later allegedly raised by the chief moderator.
"This only adds to the concerns that are being widely expressed about the window-dressing of this year's matric exam results," van der Walt said.
The DA had written to Education Minister Naledi Pandor, asking for an independent enquiry into the examinations.
However, education department spokesman Lunga Ngqengelele said uMalusi, the quality assurer of the national qualifications framework, was a credible and independent body.
"Before we release results they are assessed by uMalusi... who then will issue a report if any irregularities are suspected."
The department was still conducting its own assessment of the matric results, which was expected to be completed by the end of January.
"The completed assessment should be able to indicate if there is any truth in the teachers' allegations," Ngqengelele said.
He also called on anyone who suspected irregularities to report them to uMalusi or the department.