Senator David Van has quit the Liberal Party amid multiple allegations made against him, including claims of sexual assault by Indigenous senator Lidia Thorpe.

On Wednesday Senator Thorpe alleged Senator Van had previously sexually assaulted her, speaking out during his speech on Sex Discrimination Commissioner's report on parliamentary workplaces.

Senator Van has repeatedly denied the claims made against him.

On Thursday Peter Dutton expelled Senator Van from the Liberal's party room after additional allegations against him were made aware to the opposition leader.

Later that day Senator Thorpe spoke on her experiences of sexual assault and harassment in parliament house without naming individuals.

Also on Thursday, former Liberal senator Amanda Stoker came forward and said Senator Van grabbed her buttocks twice at a function in 2020.

Mr Dutton is understood to have suggested Senator Van resign from parliament.

In a letter sent to Victorian Liberal Party president Greg Mirabella on Saturday, Senator Van accused the party of "wholesale disregard for due process" relating to the matter.

"I resign also acknowledging the cruel irony of doing so amidst public discourse about the weaponisation of allegations and the role of the rule of law which has at its centre the presumption of innocence," he wrote, adding that he believed he had "not been afforded procedural fairness in relation to these claims".