Political blogger Paul Staines has threatened to sue Claire Perry MP after she alleged he had "sponsored" an attack on her website.
Hackers posted pornographic images on to Ms Perry's site in response to her support for "opt-out" net porn blocks.
The MP also tweeted that Staines - who writes under the name of Guido Fawkes - was "distributing porn".
The blogger said he had instructed his lawyers to write to the MP about the "defamatory" comments.
The spat is in the wake of Prime Minister David Cameron's announcement that internet service providers (ISPs) would soon be required to block pornography and other adult content unless the customer specifically asks for the filter to be turned off.
Ms Perry has been a vocal supporter of the initiative, but on Tuesday it was reported by Staines's blog that the MP's site had been breached and defaced with pornographic images.
The MP tweeted: "That well known responsible campaigner @guidofawkes has been hosting a link that distributed porn via my website."
The blogger responded to say the site did not link to the images in its story - but instead showed a screen-grab of a non-pornographic segment of the hacked page.
"Confused by technology again @claire4devizes?" Staines said.
"We deliberately didn't link to your filthy website - we just took a SFW [safe for work] screenshot."
Ms Perry then went on to tweet: "Apologies to anyone affected by the hacking of my website sponsored by @GuidoFawkes - proves so clearly what we are dealing with."
And: "Suggest you take the link down immediately Paul and go and get a life."
'Down to earth'
In a post on Wednesday, Staines said Ms Perry had gone "proper shouty crackers".
"[The allegations] are without any foundation, merit or a shred of evidence to back them up," he wrote.
"Guido suspects it is based on Perry's dislike of the blog bringing the pushy MP back down to Earth occasionally."
Staines asked his readers to vote on whether or not he should take legal action against Ms Perry's tweets - with just over 86% of respondents saying yes.
The BBC was not able to reach Ms Perry for comment on Wednesday.
Her latest tweet reads: "Hungry family means I have to rejoin the (non-Westminster) real world.
"Suggest all those bloggers [with] made-up names (bless) do the same!"