Miami Dolphins offensive line coach Chris Foerster watches as players do drills during practice. Photo: Lynne Sladky/AP

Miami Dolphins offensive line coach Chris Foerster resigned on Monday after the emergence of a video appearing to show him snorting white powder.

The 56-second video, posted on social media by a Nevada-based model, shows Foerster sniffing the substance through a rolled up $20 bill.

“I am resigning from my position with the Miami Dolphins and accept full responsibility for my actions,” Foerster said in a statement released by the Dolphins on Monday.

“I want to apologise to the organisation, and my sole focus is on getting the help that I need with the support of my family and medical professionals.”

The Dolphins said in a statement the franchise had first been made aware of the video late on Sunday.

“We were made aware of the video late last night and have no tolerance for this behaviour,” the team statement said.

Miami Dolphins head coach Adam Gase says he can't describe his reaction, but says Chris Foerster apologised to him before resigning on Monday. Photo: Alan Diaz/AP

“After speaking with Chris this morning, he accepted full responsibility and we accepted his resignation effective immediately.

“Although Chris is no longer with the organisation, we will work with him to get the help he needs during this time.”

Foerster was in the second season of a second stint with the Dolphins after 24 years in the NFL with seven different teams.

The 55-year-old was one of the highest-paid assistant coaches in the NFL, commanding a salary valued at between $2.5 million and $3 million, ESPN reported.

The model in question, Kijuana Nige, went on Facebook on Monday to defend her decision to post the video.

Dolphins head coach Adam Gase said he had spoken to Foerster on Sunday. 

“It’s not a good situation,” Gase said. “Things happen that you don’t anticipate. It’s not fun, especially when you’re close with somebody.”

Foerster is “disappointed, upset, mad at himself – it’s unfortunate”, Gase added.