US Energy Secretary Rick Perry — who oversees the country's nuclear arsenal — has fallen for an Instagram hoax.

He reposted a message claiming there was a "new Instagram rule" that would allow the social media site to "use your photos," according to images of the since-deleted post on Perry's account — which he also linked to from Twitter — that were carried by US media.

But Perry — a two-time presidential candidate and former governor of Texas — was ready.

"Instagram DOES NOT HAVE MY PERMISSION TO SHARE PHOTOS OR MESSAGES," according to the post, which billed itself as offering protection against the new rule if it was displayed on a user's account.

There was just one problem: there was no new rule.

"There's no truth to this post," BuzzFeed News quoted a spokesperson for Instagram's parent company Facebook as saying.

Perry came in for heavy criticism on social media, with various users wondering whether someone who couldn't identify an internet hoax should be in charge of nuclear arms.

"You are promoting a fake story. Do better. Or retire as Secretary of Energy. Our nuclear arsenal should be in steadier hands," one user wrote to Perry on Twitter.

The energy secretary — who once famously said he would abolish the department he now heads — then turned to Instagram again, attempting to control the fallout by poking fun at his earlier mistake.

"I give Instagram the express right to publish, distribute and/or sell any or all of my digital content posted to the account @governorperry," Perry said in a post.

"This post I made on my phone shall stand as a legally binding document, in perpetuity throughout the universe."