Liberal firebrand Michael Moore has threatened to start fracking off the coast of Donald Trump's Mar-a-Lago resort on Twitter.

The outspoken Trump critic and filmmaker made his announcement in response to a new administration proposal to increase offshore drilling for natural gas.

"Our fracking off the coast of Mar-a-Lago begins right after Labor Day," Moore said in a tweet in which he referred to his new documentary series 'Live From the Apocalypse.'

"I've already got the rig — a beautiful Halliburton G-0008 fracking system with a monster Caterpillar engine!" he wrote.

The documentary filmmaker supported Hillary Clinton in the presidential elections and has been a vocal critic of Trump since he became president.

Earlier this week, Moore said that Trump has "dementia" and is "unfit to serve" as president.

After Trump called his former chief strategist Steve Bannon "sloppy" for his interview with Michael Wolff, Moore commented that the US president was mixing up nicknames as the documentary maker had previously been dubbed "sloppy" by the commander-in-chief.

"Wait! @realDonaldTrump - On Oct 28 you gave ME the nickname "Sloppy Michael Moore" in one of your crazed tweets," Moore wrote on Twitter. "Using the same nickname for TWO people...another sign of dementia! Unfit to serve!"

In his new book 'Fire and Fury: Inside the Trump White House', Wolff writes that Bannon slammed Donald Trump Jr. for meeting with Russian officials in June 2016, describing the decision as "unpatriotic" and "treasonous."