A freedom of information (FOI) request has revealed that, six months ago, education secretary John Swinney was told the number of subjects studied by pupils by the time they left school had reduced across the entire senior phase, from S4-6.

In advance of their debate on subject choice at the Scottish Parliament today, the Conservatives have revealed the contents of an FOI  response showing Mr Swinney was informed in May that pupils were taking fewer subjects than prior to the introduction of Curriculum for Excellence and new qualifications.

However, after receiving the analysis, both first minister Nicola Sturgeon and Mr Swinney continued to insist that the curriculum was not narrowing. They argued that instead of focusing on the number of subjects pupils were taking in S4 it was necessary to view the senior phase as a three-year continuum.

Now, the FOI reveals that even when the senior phase is looked at as a whole, the number of subjects pupils are taking has fallen.

Background: First minister grilled over diminishing subject choices

Related: ‘Narrowing’ of curriculum limiting pupil choice, politicians told

Opinion: Is Scotland’s curriculum really narrowing?

Scottish government officials wrote in internal briefings that: “A range of data and information confirms that there are, on average, fewer subjects taken by pupils now than was the case prior to the introduction of CfE and the new qualifications.”

Civil servants said that, on average, school leavers entered 10 subjects in 2012-13 but, as of 2017-18, they entered only 8 subjects.

Liz Smith, Conservative shadow education secretary, said the briefing was “conclusive proof that subject choice has been reduced across the entire senior phase from S4 to S6” and called on the SNP to act.

The Scottish government recently announced recently that an independent review of the senior phase of CfE would be carried out. 

Ms Smith said: “Scottish government officials told John Swinney exactly what was going wrong in our schools but he has spent months ignoring the evidence and pretending that all is well. 

“Both Mr Swinney and Nicola Sturgeon have misled Parliament by insisting that subject choice has not been reduced when their own civil servants told them the opposite. 

“This SNP government is clearly in denial. Ministers refuse to listen, even to their own civil servants, education experts and Holyrood’s education committee.”

She added: “The Scottish Conservatives have offered constructive solutions to fix the serious issues afflicting the curriculum, and it is past time that the SNP listened and acted before the situation becomes any worse.”

A Scottish government spokesman said: “These claims are wrong - in fact, the number of courses on offer to pupils has increased.

“This analysis takes no account of differences before and after the introduction of Curriculum for Excellence, which helps equip pupils with the knowledge, skills and attributes needed for life in the 21st century. It means pupils learn a wide range of subjects up to S3. Schools then have the freedom to design a set of courses, qualifications and awards between S4 and S6, tailored to meet young people’s needs.

“Young people can choose from a much broader range of pathways than before. What matters is the qualifications that pupils leave school with and last year a record proportion went on to positive destinations including work, training or further study.”