Liberal Democrat peer Lord Rennard has given the party hierarchy until Thursday this week to lift his suspension before he commences legal action, reports the BBC.
The Liberal Democrat peer and former party Chief Executive was suspended last year after four former colleagues claimed that he had sexually harassed them whilst working with him in the past.
The peer has always denied the claims, but an internal investigation by the party concluded that whilst the standard of proof for a legal case against him was unlikely to be met, the allegations were credible and he should apologise for any harm caused by his actions.
Lord Rennard has resolutely refused to apologise, and as a result was deemed to have brought the party into disrepute, with a suspension deemed necessary by the party whilst the disrepute charge was investigated.
Lord Rennard wants to return to his seat in the House of Lords, and believes that his suspension is unlawful because it flouts the party's own rules and constitution.
It is understood that if the suspension is not lifted by Thursday, Lord Rennard will seek a court injunction to overturn the suspension, allowing him to return to the Lords.
Among the allegations of harassment are those made by Bridget Harris, a former aide to Nick Clegg, who claims that Rennard placed a hand on her knee and suggested they finish their coffees in his room after a meeting at a hotel.
Harris has so far refused to rule out a civil legal action against Rennard should the party's disciplinary process not mete out sufficient justice.
"In terms of civil action, how can I possibly say... what I would or wouldn't do, depending on the circumstances," she told BBC radio.
Lord Rennard says he regrets any offence caused by his actions, but has refused