In the interest of balance, I was reading a paper this week from UCL, which looked at payroll taxes in Norway. Long story short, they had previously imposed lower payroll taxes in less populated parts of the country to try and encourage businesses in those regions, but it was banned by the EU in (I think) 2004, with the new law saying that taxes had to be uniform across a territory. Analysing the before and after, the data found weaker business growth in regions where taxes were increased, with slightly lower wages also (the caveat being that the analysis was restricted to large employers, as the Norwegian government were able to subsidise things for smaller employers so they were basically not required to pay payroll tax).
Anyway, I've seen similar suggestions this week in Scotland about VAT (they want to impose a lower level than the rest of the UK I think), but would have been barred from doing so during our EU membership. It's possible that there are justifiable reasons for this measure, but it seems a strange one to me, especially as geographic inequality is an issue in most countries in Europe, so being able to charge lower taxes to stimulate growth in those poorer regions would seem sensible.