More to follow later – at the moment I don’t have access to the statement that was released to the media, and I’m, er, off to the theatre. But it has been confirmed, and a statement has been released.
UPDATE: Thanks to Jonathan Davies for posting the statement in the comments. The Independent has a story on the resignation which says:
The row was potentially damaging for Sir Menzies, who has insisted that voting reform is a top priority. He will attempt to limit the fall-out from the row today, using a speech to the party’s Welsh conference to declare that the party still regards proportional representation as an overriding priority. He will declare: “Be in no doubt that my commitment to proportional representation – for every election – is absolute.”
Iain Dale has also picked this up, and it looks like some anonymous Lib Dems have made some comments.