Former LibDems' chief executive Lord Rennard was suspended on January 20 pending an investigation into whether he had brought the party into disrepute by failing to apologise to a number of women who had made complaints against him.
A QC's inquiry into the allegations concluded the women's claims were credi- ble but there was insufficient evidence to bring disciplinary charges. The inquiry suggested the peer should make an apology, prompting LibDems' leader Nick Clegg to tell him: "No apology, no whip."
Lord Rennard offered to take part in mediation with the party and the complainants, but also instructed a QC specialising in public law to advise him on the "law- fulness or otherwise" of the decision to launch a second inquiry into his conduct.
The letter before action served on party HQ is understood to name individuals involved in the suspension decision, including the chairman of the LibDems' regional parties committee Mike Wheatley and the chairman of the English Council of LibDems Peter Ellis.