Lisa MacPhail appealed against her grades

They allege that the appeals were not properly heard by the exams body, and that the Scottish Executive failed to sort out the problem.

The students include Lisa MacPhail, who did not get her expected A pass in art - and failed to get the award upgraded on appeal.

"I just felt devastated, because I was really counting on the appeal," she said.

"I thought that when they relooked at their papers they would realise that they had made a mistake and everything would be okay."

'Not impartial'

Lawyer Cameron Fyfe, who is acting on behalf of 36 pupils, said he had written to Education Minister Jack McConnell asking him to intervene.

He has asked for the exam papers to be returned to either the pupils or their schools so they can be assessed by an independent body.

If the request to the minister was unsuccessful, Mr Fyfe said he would bring a test case in the Court of Session in Edinburgh arguing that the SQA was in breach of the European Convention of Human Rights.

"It is in charge of the initial results and also the appeal results, and therefore is not independent and is not impartial, which it has to be under the convention," he said.

Appeals reached double their normal level

The SQA said it could not comment until the case came to court, while Mr McConnell said the interpretation of the convention was a legal matter and not one for the Scottish Executive.

The action against the SQA is the latest development in the exams crisis which hit students in Scotland.

A report on the fiasco published last week concluded that the problems were worse than previously thought and that the results system came within a whisker of collapse.

An inquiry by the Scottish Parliament's Education Committee found there were serious failures at board and management level within the SQA.

Appeals process

The qualifications system was thrown into chaos when thousands of pupils received delayed or inaccurate Higher and Standard Grade results.

The controversy continued into the appeals process.

The SQA had promised to complete all non-urgent appeals by 31 October, but failed to meet the deadline for the 40,800 appeals - double the usual number.

Interim chief executive Bill Morton - who apologised for the failure - told a parliamentary inquiry into the exams crisis that he had been unaware of the problem.

Pupils received late or inaccurate certificates

Last week Scottish head teachers expressed concerns that so few exam result appeals had been granted.

They called on the SQA to explain its actions and estimated that hundreds of youngsters had lost out.

The Headteachers' Association of Scotland said parents had expressed concerns that students who had sailed through their prelims were awarded below-par grades.

First Minister Henry McLeish gave a personal pledge on Sunday that there would not be a repeat of the crisis.

He told BBC Scotland's Holyrood programme: "This is a unique situation, but I want to say that it will never happen again because of the actions that we are taking."