Senior Liberal Democrats have pledged to act following what they say are "very serious allegations" against one of the leading figures in the party.
Two separate investigations are underway after a Channel 4 News report made allegations of sexual harassment against Lord Rennard, the former chief executive of the Liberal Democrats.
Lord Rennard issued a fresh denial of the claims, telling Channel 4 News he was "disappointed and angry" by the allegations, which were "absolutely denied".
On Friday, Channel 4 News broadcast allegations from two more women. The party is accused of not taking their complaints seriously.
Party president Tim Farron, who is leading one of the internal investigations, told the programme: "Clearly there is a case to be answered.
"There is a particular case..the disciplinary procedure that will be gone through with regard to Lord Rennard and the very serious allegations made against him.
"There is also a wider issue for the party, that absolutely must be taken seriously, which is that there could well have been a series of complaints made over a series of years that were not taken seriously or were not taken forward."
Deputy leader Simon Hughes said the party had responded "as quickly and effectively" as it could do after the allegations were broadcast by Channel 4.
He added: "There should be a formal inquiry. These are serious allegations and need to be dealt with quickly, but they need to be dealt with properly and none of use should jump to any conclusions until that investigation is complete."
In his statement released to Channel 4, Lord Rennard said: "I absolutely deny any suggestion of improper touching, nor did I invite a woman to join me in my room.
"I note that these alleged instances supposedly took place in public bars with other people present.
"I am disappointed and angry that anonymous accusations from several years ago are once again being made public in this manner in a clear attempt to damage my reputation.
"Let me reiterate that in 27 years working for the Liberal Democrat party, not a single personal complaint was ever made against me to my knowledge."