Merlin Entertainments has blamed terror attacks in the UK for lower visitor numbers at attractions such as Madame Tussauds and the London Eye.
The firm which also runs the Legoland theme park, warned that numbers could continue to fall domestically.
It said: ‘The attacks in Manchester and London over the past month have resulted in a further deterioration in domestic demand and, given the typical lag between holiday bookings and visitation, we are also cautious on trends in foreign visitation over the coming months.’
Trading at its UK theme parks, which includes Thorpe Park and Alton Towers, have been ‘adversely affected in recent weeks by the terror attack’.
Shares in Merlin fell 2.4 per cent in morning trading as investors digested the update.
Nevertheless boss Nick Varney remained defiant as he anticipated London to bounce back.
He said: ‘What is clear, however, is that London has bounced back before, and will do again. I have every confidence in the longer-term resilience and growth trajectory of the market. London is very much open for business, welcoming visitors from the UK and from around the world to this exciting and vibrant city.’
Meanwhile trading at Merlin’s Legoland Parks and theme parks – such as Alton Towers – has been in line with expectations.
Two years ago sixteen people were injured in the June 2015 crash at Alton Towers.
Investors and analysts heeded little comfort from this morning’s update despite the company being in the midst of an ambitious global expansion, which includes building new Legoland parks across the world.
Neil Wilson, senior market analyst at ETX Capital, said: ‘Merlin had already warned in March when it released its 2016 full-year preliminary results that the threat of terror attacks had hit its UK business, citing events in Paris and Brussels as having an impact.
‘But it is worth noting Merlin is only about a third of the way through a planned global expansion of Legoland.
‘There ought to be considerable new revenue streams coming in the longer term that investors who are worried about terror threats to the UK business in the near-term may want to look more closely at.’