Scotland's exams body has been urged to step up its quality control procedures after a report found a number of "typographical and coding errors" in a computing paper.

This summer's National 5 computing science exam was criticised by some teachers, who warned there had been a number of problems with questions.

The Scottish Qualifications Authority (SQA) said there had been "a small number of typographical errors" in the paper.

READ MORE: Examiners admit to coding errors in computing exam

Now an official report into the exam written by the principal assessor for the subject has found there were a number of "coding errors" in the paper too, while one question contained an error which "did not allow it to be answered as originally designed".

The report notes that grade boundary adjustments were made to ensure no candidates were advantaged or disadvantaged by the errors.

Education Secretary John Swinney wrote to Dr Janet Brown, chief examiner in Scotland, in June to express his concerns.

READ MORE: Examiners admit to coding errors in computing exam

At the time he told MSPs: "I think, frankly, that is not good enough, these issues should be checked properly, there is adequate opportunity for this to be done and I have made clear my discontent about that to the chief examiner."

The report into the exam has prompted fresh calls from opposition parties for the SQA to ensure exams are "watertight".

Scottish Conservative shadow education secretary Liz Smith said: "Every parent, pupil and teacher and every college, university and business across Scotland needs an absolute guarantee that the SQA exam system is 100% watertight when it comes to quality assurance.

READ MORE: Examiners admit to coding errors in computing exam

"They need to have complete confidence in the system and that in turn means there has to be strong quality assurance which prevents mistakes being made in the setting of papers, their verification and their marking.

"It is simply not good enough that these errors are appearing despite all the guarantees provided by the SQA that mistakes will not happen again."

Scottish Liberal Democrat education spokesman Tavish Scott said: "Reports of mistakes in this year's National 5 computing tests are a huge concern.

"Whether we are talking about the content of questions or their marking, pupils need to know that their exams will be handled fairly. This is the latest in a series of exam problems reported by the SQA.

"They need to take urgent action to ensure proper safeguards against errors are in place."

READ MORE: Examiners admit to coding errors in computing exam

Labour education spokesman Iain Gray said: "Computing and other science subjects are absolutely vital for the long-term future of our economy, mistakes like this simply cannot be allowed to happen."

Dr Gill Stewart, SQA director of qualifications development, said: "As we do every year, we consider what went well in the most recent diet, and where improvements could be made for the future by SQA and the education system.

"Our course reports, which are provided for all subjects at all levels, also highlight ways in which recent exams and coursework may have differed from those of previous years.

"This is to ensure standards are maintained. We are committed to the continuous development and improvement of our qualifications and assessments for the benefit of all candidates."