Apparently not:

"HMRC can prosecute tax advisers if they try to hide schemes, but has no sanction against those that create and sell artificial trading arrangements designed solely to dodge taxes."

That's what she wants to change.

This sounds like something that isn't defined as illegal yet but might be in the grey area - and if HMRC decides it's illegal later then you are punished ex post facto.

Definitions!

llegal tax avoidance = tax evasion. You might as well talk about legal tax evasion.