IT was one of the most awkward moments Scotland's Education Secretary has had on television.

Last month, Michael Russell was in the BBC's Newsnight Scotland studio to discuss the progress or otherwise of the SNP's commitment to reduce class sizes.

In its 2007 manifesto, the SNP promised to deliver class sizes of 18 or fewer in each of the first three years of primary school. Unfortunately for the SNP, figures published in December showed the situation is the worst it has been since they took power.

There are 22,992 P1-P3 pupils in class sizes of 18 or fewer compared to 23,563 in 2007/08 - the first year the SNP could argue they had an influence on policy. Similarly, average class sizes were 22.8 in 2007/08 for P1-P3 pupils compared to 23.2 now.

Understandably, programme presenter Gordon Brewer was keen to point this out to Mr Russell, but he was having none of it, preferring instead to refer back to 2006/07 - the year when the previous Labour-led Scottish Government was in power.

"What undoubtedly is true is the class sizes in the early years are lower than they were in 2006 and 2007 when we came into power. We have still got lower class sizes than we inherited," said Mr Russell.

In fact, only in the first year of primary is this the case, with average class sizes of 21.2 compared to 23.1 in 2006/07. In both the second and third years of primary, average class sizes have actually gone up.

An exasperated Brewer finally gave up his line of questioning telling Mr Russell: "You must be working on some weird theory of statistics that your own statisticians aren't working on. There is a basic question about openness of politicians with the public here."

Politicians refusing to give direct answers to difficult questions, or choosing their own question to answer, is nothing new, but the public surely deserves a better explanation of what has gone wrong with the SNP's class size policy than an ultimately meaningless argument over two different sets of figures.

It is not a new phenomenon. There has been an equally distracting debate in recent times about the number of students being admitted to Scottish colleges. On Wednesday, the Scottish Conservatives published figures that show the number of women entering college has fallen as a result of a Government policy that colleges should focus on full-time courses for younger learners to cut youth unemployment.

The Conservative figures are based on the number of individual learners going through the doors of colleges in any one year, regardless of the length of their course, but the SNP countered by using figures which measure the overall number of hours colleges spend teaching women - which is roughly the same as it was in 2007.

Both Audit Scotland and the Scottish Funding Council have said the SNP's policy has reduced the number of students attending college, with women and older students most affected, but it is still difficult for the public to judge the SNP's stewardship of further education when its case is based on using different figures rather than explaining the consequences of its strategy.