Ministers (and their Shadow counterparts) do from time to time resign. They may do so because they don’t intend to seek reelection to Parliament (e.g. William Hague), they may have personal problems (Alan Johnson) or they may resign before they are pushed or on a point of principle e.g. Robin Cook and Claire Short both resigned over the decision to go to war in Iraq in 2003.
However it is unusual for a minister to resign on the grounds that he doesn’t like the Cabinet Minister who is in charge of him. However, as the cracks begin to show in the coalition that seems to be exactly what Lewes MP Norman Baker has done. Frustrated by the failure of Theresa May to take heed of his suggestions on drug law reform and embittered because May allegedly perceives the Lib Dems as ‘cuckoos in the nest’. Norman Baker has quite his role as Home Office Minister (it may also be to allow him extra time to defend his Lewes seat in the 2015 election…)
This piece in the Guardian summarises Baker’s position and looks at some of the potential pitfalls of coalition government…