The Deloitte report on promotion and relegation in United States professional soccer has "serious credibility questions", according to Major League Soccer Deputy Commissioner Mark Abbott.

Earlier on Monday a summary of a wider report was published, which laid out the benefits of introducing a pyramid system in the US.

Dan Jones, Head of the Sport Business Group at Deloitte, said of the report’s findings: “US soccer has a major opportunity to capitalise on the nation’s growing interest in soccer.

"We believe the introduction of promotion and relegation into the existing league system could have numerous long-term benefits, including increased attendances, increased broadcast audiences, improved commercial revenue and a positive impact on both elite players and grassroots participants.

“Though the US soccer league system may not be ready for such a move immediately and its implementation may not appear urgent, the topic is worthy of greater exploration and debate.

"US soccer should properly consider the merits of introduction of promotion and relegation and a transition plan for its successful introduction in order to drive US soccer forward.”