Venue bosses at the Edinburgh Fringe festival have voiced concern that the event has outgrown its audience.

William Burdett-Coutts, director of the Assembly, the festival’s largest theatre operation, said that competition for audiences is now too tough.

“Even great shows, with great reviews, have not been getting the crowds. It's the first time I have felt there are too many shows in Edinburgh.”

Ed Bartlam, co-director of Underbelly, which has more than 140 shows playing in 12 perfomance spaces, said that growing the audience to meet the expansion of the Fringe was a priority.

“Ticket sales have been very strong but we can’t avoid the fact that as the festival grows, the audience will need to grow to meet it, which means improving promotion, infrastructure and accommodation.”

“It’s good that the festival is evolving, but the challenge is to get the audience up to meet it.”

There are more than 2,000 shows at the Fringe this year, 10 per cent more than in 2006. The event has doubled in size in the past five years.

Mr Burdett-Coutts began working with the Assembly Rooms on George Street more than 25 years ago. This year his empire has grown to eight venues around Edinburgh with 144 shows and a total of 700,000 tickets to sell during the festival.

“I’m as guilty as anyone else. There is a limited local audience. We have expanded our shows,” he said. Sales are down 10 per cent in terms of where they should be, Mr Burdett-Coutts added.

Mike Griffiths, the administrative director of the Traverse theatre, said that ticket sales had been more sluggish than in previous years but were now starting to accelerate.

“There is a lot more competition. In the past four-star shows would have started to move quite quickly and five-star shows would have gone. It has been a lot slower, I’m not sure why.”

Paul Lucas, a publicist and promoter who is involved in eight shows this year, said: “There's a lot of us and we are all vying for the same attention in the press, the same attention from the promoters. It does feel a little thinly spread.”

Anthony Alderson, the director of the Pleasance venue, with 185 shows, said that across the board, sales appeared to be better than last year. But some of the bigger projects were suffering, including Stonewall, the venue's extravagant musical play about the riots in New York that were a turning point for the gay rights movement.

“It’s a great Festival show, it’s had some fantastic reviews and it’s not doing the kind of business I would expect it to be doing. It’s playing to 40 per cent houses.”

“I do think we’ve reached capacity, I’m not sure we can get any bigger. There’s a finite number of people we can keep bringing into Edinburgh, and that band of people gets thinner across more events. I think it’s got to the upper limit, and we need to be careful. if it gets too thin, then companies stop coming.”