Andy Murray suggested opponent Fernando Verdasco was lying after a row over illicit coaching erupted following their second-round clash at the US Open.

The high temperatures and humidity in New York this week led tournament organisers to introduce a new rule permitting a 10-minute break between the third and fourth sets during men’s matches.

Players are not allowed to talk to their coaches, which is exactly what Murray said he saw Verdasco doing after finishing a cold shower.

The Scot was furious that it was he who alerted officials to the incident, telling umpire Nico Helwerth when he returned to the court: “I had to tell them because no-one knows the f***ing rules.”

Discussing the matter, after Verdasco’s 7-5, 2-6, 6-4, 6-4 victory, Murray said: “I went and told the supervisor. I said, ‘What are you guys doing? I mean, there’s clear rules here and you’re allowing this to take place. I don’t get it.’

“Then he ran through, ‘Oh, you’re not allowed to speak.’ They obviously weren’t in there for long, but you’ve got to do better than that. This is one of the biggest events in the world.”

Speaking about what actually happened in the dressing room, Murray said: "When I came out of the shower, his coach and his -- I don't know if he's playing doubles with him, but one of the Spanish doubles players was in there chatting to him, and you're not allowed to speak to your coach. I went and told the supervisor.

Verdasco flatly denied any such rule breach had taken place, claiming that while his coach was in the locker room, he spoke only to another player, Marcos Baghdatis, and the Cypriot’s coach.

When asked for his take on what happened behind closed doors, Verdasco said: "I know the rule exactly. I didn't speak anything to any member of my team.

"I know you can't talk with your team or use the phone or use anything. Is like a break on the court, but just on the locker. I saw my coach in the locker room, but I didn't even talk one word with him. I think he went to the toilet. I obviously cannot say, Don't go to the toilet. But actually we didn't even spoke one word.

"I was in the ice bath with [Marcos] Baghdatis and his coach. The guy from the court with the time behind me just because I was asking him, Please tell me the time so I don't get late.

"Andy didn't take an ice bath, because I told Marcos -- I was first. I didn't even know Andy was coming. I told Marcos when I saw Andy, Maybe he's coming. Andy said, No, I'm not taking ice bath. I said, Marcos, you can stay.

"I went in, I saw my coach, we didn't talk one word. I just dress up quickly and went back to the court. Obviously, if you say or Andy say that, I don't want to say that he lie, but I didn't talk one word with my coach or any one member of my team. I know exactly the rule and I don't want to be the one breaking it.

"But I don't know why Andy said that. Maybe because he saw my coach, he thought that I was speaking with him. Like I said, he went to the toilet, not to talk to me."

With tournament organisers apparently unable to shed any light on what happened, it was a case of one man’s word against the other – and Murray was determined to make sure it was he who had the last one.

In a post on Instagram, Murray wrote: “I’m off to get a health check as apparently I’ve started imagining things,” followed by the hashtag #liarliarpantsonfire.

Nick Kyrgios, who has history with Verdasco, also weighed in on the debate, saying of the coaching accusations on Twitter: “Let’s be real, very believable because it is Verdasco lol.”