A lack of access to funding and increased competition has left clubs struggling to compete with late-night bars and pubs, according to commercial lender Ortus Secured Finance.
Turnover at nightclubs has been falling continuously over the last three years. Last year, the top 100 nightclubs posted revenues of £340m, down from £373m the year before.
The boom in late-opening bars and clubs as a result of the 2003 Licensing Act has had a big knock-on effect on the country's biggest discotheques.
"The economic downturn together with the introduction of new licensing laws hit the nightclub industry hard," Jon Salisbury, managing director of Ortus Secured Finance said.
"Nightclubs have struggled to secure the funding they need in order to compete with this new wave of venues. While there has been a transitional period over the last few years many nightclubs continue to need funding in order to renovate, buy new equipment or even diversify to include restaurants and bars, for example."
Read more: Britain's economy needs more clubbers
The Night Tube, which finally arrives on 19 August, could aid the nightclub sector, though it is too early to predict its precise impact.
In a 2014 report, Transport for London said the Night Tube "will open London's night-time economy to a whole host of new opportunities, altering the way that businesses choose to operate".