The post includes statements that Lawson "wilfully misled the public, acquaintances and others by knowingly orchestrating an 'assault' as a cynical PR exercise."
Lawson's law firm also demanded an "immediate publication of an apology" on his Twitter account.
It also threatened legal action if the claims are not taken down by Hillgrove.
However, the PR expert said that he had obviously touched a nerve and it's not a crime to have a difference of opinion.
Hillgrove also said that he will not remove his original blog.