The senior Liberal Democrat peer Lord Rennard's solicitors said in a statement:
Liberal Democrat peer Lord Rennard has been interviewed by the Metropolitan Police under caution after he voluntarily attended a south London police station by appointment today.
Nick Clegg will appeal for frustrated Liberal Democrat activists to "move on" from damaging rows over the NHS and tuition fees.
The Deputy Prime Minister insisted there could be "no more looking back" and party members should be "shouting our achievements from the rooftops."
The exhortation comes as the Lib Dems kick off what could be another fractious spring conference in Gateshead. Last year's event was dominated by dissent over the coalition's controversial health shake-up.
he legislation was "paused" as a result of the outcry and opposition from NHS workers, and has since been amended more than a thousand times.The conference is expected to vote to consider a topical motion on the NHS on Sunday, which could prove embarrassing for Mr Clegg.