With opinion polls showing that the Liberal Democrats are likely to have a role in an administration led by Labour or the SNP, Mr Gorrie said that wide consultation should precede legislation. “Educational initiatives should fit into a long-term plan as happens in some other countries where the school system performs better.”

He was speaking as the party revealed the findings of a questionnaire sent to primary headteachers which showed that reducing “hassle” was one of the top priorities. Heads wanted more support and less blame from politicians.

Despite the Government’s commitment to reducing primary class sizes, 41 per cent reported larger classes and 68 per cent said they received fewer hours from visiting specialists. More than half said the amount of money for books and equipment had gone down in recent years.

There was virtually no support for selective pay increases to improve teacher morale. Moreover, increasing pay across the board was slightly less favoured than reducing the volume of paperwork. “It’s about time we started being recognised as very hard working, first-rate professionals - we do an average of 16 hours unpaid work a week,” one respondent commented.

A third of heads said that the best answer to pupil disruption would be to target more resources at the earliest stage of problems. Only 11 per cent wanted special units outwith schools and 14 per cent units within schools.

The survey was sent to 2,352 schools and there were 529 responses. Mr Gorrie said that at least eight Labour and SNP councils had issued gagging orders to dissuade heads from taking part.

The Liberal Democrats will use evidence from the survey and a similar one sent to secondary heads in drawing up their education manifesto for the Scottish parliament election.