Hotel occupancy rates in Dublin City for October are currently as low as 10 per cent, while they are highest in the South East at 38 per cent.
It comes as the 'Stay and Spend' scheme kicked off today, which offers up to €125 in income tax credits for those staying in hotels or eating out between now and the end of April next year.
According to the IHF, 100,000 jobs have been lost so far this year, with a further 100,000 jobs at immediate risk.
IHF chief executive Tim Fenn said: “The situation has now deteriorated further in recent days, and we have reached a critical point with cancellations wiping out all new business generated over the week.
"Effectively, no net new business has been generated over the last seven days for the country as a whole – the first time this has happened since the sector reopened at the end of June."
Mr Fenn added: “The collapse in new bookings is extremely worrying and adds to an already exceptionally challenging environment. It is a direct consequence of additional Government restrictions and points to a very difficult number of months ahead.
"This must be recognised by the Government in the upcoming Budget. Existing supports for the tourism industry are totally inadequate given the current restrictions.
"Urgent and unprecedented intervention by the Government is essential to support tourism and safeguard the thousands of jobs that are at risk. "