Ed Sheeran said he’d have to be an “idiot” to rip off Marvin Gaye’s song “Let’s Get it On” and then perform it for thousands of fans — growing agitated as he was grilled on the stand Tuesday in a federal lawsuit accusing him of copyright infringement.

The British singer-songwriter attempted to rebuff claims that a video of him performing a mash-up version of Gaye’s 1973 R&B classic and his own Grammy-winning track “Thinking Out Loud” at a 2014 concert amounted to a “confession.”

“If I had done what you are accusing me of doing, I would be quite an idiot to stand on a stage in front of 20,000 people and do that,” an irate Sheeran, 32, said in Manhattan federal court.

The “Shape of You” singer had a tense back and forth with Keisha Rice, an attorney for the heirs of the late Ed Townsend — Gaye’s co-writer on the soul track — who filed suit against Sheeran in 2017.

During opening statements, another of the plaintiffs’ attorneys, Ben Crump, argued Sheeran made a “confession” when he combined both hit songs during a live performance in Zurich, Switzerland.

A clip was shown in the courtroom of Sheeran bouncing back and forth between his “Thinking Out Loud” and “Let’s Get it On” — with Crump calling the video the case’s “smoking gun.”

But when he was called to the stand by Rice, the pop star attempted to downplay the supposed significance of the performance.

“I mash up songs at a lot of gigs,” said Sheeran, who also testified that he’d first heard Gaye’s classic in 1997’s “Austin Powers.”

Sheeran’s frustration came after he was peppered with questions about his musical education, and whether he took classes on musical plagiarism.

“I did not take a degree on plagiarism,” fired Sheeran.

He argued that the chord progression in question – 1-3-4-5 – is common in pop songs and that artists often mash songs together, particularly mentioning The Beatles’ “Let It Be”.

“When you’re playing a song live and it fits in the same key, most pop songs revolve in the same three or four chords,” Sheeran said.

Rice and Sheeran volleyed awkwardly, including a moment where the singer asked for Google to be used to read lyrics of a song of his that the plaintiffs’ attorney had recited during her questioning.

His lawyers argued in their opening statement that the chord progression in “Let’s Get it On” had been used in other songs before Townsend collaborated with Gaye on the 1973 track.

“[From] Buddy Holly to The Beach Boys to The Bee Gees to Elton John… have used this chord progression before Ed Townsend,” Sheeran attorney Ilene Farkas said, arguing that the chord progression was taught in basic how-to-play piano books, including one published in 1967– six years before Gaye’s R&B hit.

Experts for both sides are expected to take the stand on Wednesday when Sheeran’s “Thinking Out Loud” co-writer Amy Wadge is also set to testify.