A US rock star has apologised to doctors and nurses at the Whittington Hospital after he publicly blasted them for making him wait in line at A&E “regardless of telling them an audience was waiting for our show to begin”.

Former Dream Theater drummer Mike Portnoy became embroiled in an online spat with UK fans and staff at the Archway hospital after being taken ill just hours before he was due to go on stage with rock band Neal Morse.

Leaving the Whittington Hospital on Saturday evening without treatment, he complained the experience left him to play “in the worst physical condition of my life”.

He posted on his Facebook page: “A very special NO THANKS to the staff at the Whittington Hospital for NOT seeing me regardless of telling them that there is an audience waiting for our show to begin. I finally left WITHOUT seeing a doctor in order to make tonight’s show. I have no idea how the hell I’m going to make it through this show. I can’t even stand up or lift my arms.”

He was due to perform for waiting fans at nearby Islington Assembly Hall.

But sympathy for the award-winning US rocker – who was the second youngest person to be inducted into the Rock Drummer Hall of Fame – was not forthcoming from all.

His complaint generated more than 3,000 comments in under 24 hours, with some suggesting he was trying to use his fame to get better treatment on the NHS – something he later vehemently denied.

One fan wrote: “Not to be rude, but if someone was dying, I’d hope they didn’t move you to the front of the line just to get you to a show. Very narcissistic thinking here.”

Another fan, claiming to be a doctor at the Whittington, added: “As much as I’d jump at the opportunity to help you if I actually was on call tonight, please try to understand.

“Us healthcare professionals don’t want anyone to wait or suffer at all, however we encounter life-threatening conditions every hour, sometimes every minute, that stop us from seeing others that may be slightly less unwell as quickly as we’d like.

“With all the respect I have for you, it hurts when one of my idols insults an organisation I work very hard for. Waiting sucks, I know, but dying patients suck even more.”

Mr Portnoy later apologised to staff members at the Whittington, adding: “It was not a personal attack or rage against England’s health care system in general, of which I know nothing about. I did not expect any special treatment or want to be put ahead of anybody else in need. We only wanted some answers as the clock was ticking until showtime.”

Hours before the incident, serious questions were raised over how an ambulance called to aid the musician ran out of enough petrol to get him to hospital – leaving him to beg his own fans to drive him.

Fellow bandmember Neal Morse recalled: “The paramedics said Mike should go to the hospital and loaded him in the ambulance. They ran vitals. Then, after some time the driver said they were too low on fuel and suggested alternate transport. Shocked and in a bit of a panic, I ran into the venue and asked if anyone had a car. We got a ride from a very kind fan and it took us 30 minutes because of traffic that the ambulance probably could have avoided.”

A spokesman from the London Ambulance Service later told the Ham&High the ambulance crew “had been on the road since 6.30am and it was their last job”. The spokesman added: “The vehicle was low on fuel and staff requested another ambulance to take the patient to hospital.”