The actor, 62, who plays newly elected UK Prime Minister David in the film, said he thought he would “hate doing that” when he first read the script.
In the scene he dances emphatically round the offices of Number 10 to The Pointer Sisters’ 1983 hit Jump, before being caught by a personal secretary.
The dance has been imitated by internet users for almost 20 years since the film’s release, with many users emulating Grant’s snake-hipped moves.
Speaking to ABC news anchor Diane Sawyer during a special 20-years-later celebration of Love Actually, Grant admitted that “some people like (the scene)”.
“I think I saw it in the script and thought ‘I’ll hate doing that’. No Englishman can dance when they’re sober at 8am in the morning,” he said.
“And to this day, you know, there’s many people, and I agree with them, and we think it’s the most excruciating scene ever committed to celluloid.
“But then some people like it.”
The actor also claimed it had been his idea to have the secretary, played by the late Meg Wynn Owen, catch him mid-boogie.
“I will give myself the credit of having the secretary catch me… genius,” he said, laughing.
The film’s writer Richard Curtis said Grant was “grumpy” about performing the routine, but went through with it due to “contractual obligation”.
“I think he was hoping I (would) get ill or something and they’d say, ‘Oh, what a shame to lose that dancing sequence’.
“He was grumpy but he knew he was under a contractual obligation.”
The Laughter & Secrets of Love Actually: 20 Years Later, was broadcast on US network ABC on Wednesday.