RTÉ News understands that about 20 staff have locked themselves into a room in the company's office on Grafton Street after being told that they are to lose their jobs today.
Ciaran Shortall, customer services manager at Thomas Cook in Grafton Street, says that staff were told last week that the Dublin office was to close on September 6.
However following a protest last week, he says, staff are being told today that the company has brought forward the closure of its two Dublin offices, and are being asked to leave the premises immediately.
Mr Shortall says staff are refusing to leave, and will stay as long as they have to in order to resolve the matter.
A spokesperson for Thomas Cook has confirmed that its two Dublin stores - on Grafton Street and North Earl Street - are to close today, with most of the 44 staff are to lose their jobs.
He said staff meetings are taking place now. He also confirmed that the closure was originally scheduled to take place on September 6.
'Following more than two months of consultation, it is with regret that we have now reached the decision to continue with plans to close the two Thomas Cook stores,' the spokesman said.
'During this time we have considered several alternatives to make the two stores profitable but unfortunately these have not proved to be viable,' he added.
'Our priority is to contact customers with bookings made through the two stores to let them know how to contact us and to make arrangements for the collection of travel documentation,' he concluded.
