1. Transport (8)
2. Chief Secretary (7)
=3. Defence (6)
=3. Scotland (6)
=3. Energy (6)
What's just as interesting is how much less stable government has been during this period than compared to roughly the same period before it.
Comparing the turnover in posts over the period since the 1997 General Election - a slightly longer period by a few months but the same number of actual elections (2) - reveals that while one might expect the earlier period to have had a marginally higher number of Cabinet Minister turnovers (because it is literally longer) - in fact, the opposite is true.
Cabinet Ministers in Post 1997 - 2005: 64
Cabinet Ministers in Post 2005 - 2012: 104
I have kept the same posts in both posts, making comparisons where necessary ( eg. DTI became BIS, Constitutional Affairs became Justice etc).
Quite an amazing difference
Now, there has been a change of government in the second list so you might expect the second to be higher on that basis, as a whole cabinet had to change in May 2010; but that still only accounts for 22 posts; so the later turnover remains significantly higher.
Other points of interest
Chief Secretary still had one of the highest turnovers of post in the first period I looked at - equal first (with leader of the Commons) at 5 changes
Only one single department has more people in post in the first period than the second. Which? Surprisingly it was Tony Blair's 'biggest priority' - Education.
Home Secretary was still a stable post in the first period - just 3 people in post during the period. It's not the graveyard everyone says it is...
Here's the comparison (click to enlarge)
Blue = 2005-2012
Red = 1997 - 2005