Liberal Senator Linda Reynolds has made good on her threat to sue Brittany Higgins over social media posts by the former staffer.

In a writ lodged in the West Australian Supreme Court on Monday, Ms Higgins is accused of posting defamatory material about the senator on her Instagram and Twitter accounts.

The posts were allegedly published on July 4 and 20, according to the document seen by AAP.

Senator Reynolds is also claiming a breach of contract over the contents of the Instagram post.

The senator and Ms Higgins entered into a deed of settlement and release in March, which contained a “non-disparagement” clause.

Senator Reynolds will seek aggravated damages plus interest and costs, and an injunction restraining Ms Higgins from publishing further allegedly defamatory material.

Lawyers for the senator contacted Ms Higgins in early July advising her to remove the allegedly defamatory posts or potentially face legal action.

Ms Higgins tweeted in response that she was considering her legal options. 

Ms Higgins alleged she was raped in 2019 by Bruce Lehrmann inside the ministerial office of Senator Reynolds, for whom they both worked as staffers.

Mr Lehrmann consistently denied the allegation, and his trial in the ACT Supreme Court was derailed by juror misconduct.

Prosecutors decided not to pursue further action, citing concerns of the impact it may have on Ms Higgins’ mental health.

Senator Reynolds has previously said she had been the target of “unwarranted criticism and abuse” ever since Ms Higgins went public with the allegation against Mr Lehrmann.

“Despite her repeated defamation of my character, until now I have not taken any action against her personally – even though I considered her words to breach our previous settlement agreement,” the senator said in a statement in July.

Senator Reynolds is also pursuing action against Ms Higgins’ partner David Sharaz over five allegedly defamatory social media posts.