Nusrat Sahar Abbasi, an MP in Sindh province, spoke of her fury after provincial minister Imdad Pitafi invited her to his private chambers on the floor of the assembly Friday.
The female MP told AFP that the widely-publicised incident shows how laws to protect women are not being enforced.
She said she protested strongly but the deputy speaker of the assembly, also a woman, refused to take any action.
A frustrated Abbasi was then pictured Saturday holding a small bottle said to be of petrol and threatening to self-immolate if action was not taken.
Federal party chiefs were forced to intervene as the incident exploded on social media, with Pitafi finally caving to the pressure and apologising in the assembly while offering Abbasi a chador, or veil, as a mark of his respect.