The Space Centre in Preston thought it had secured Â£800,000 in grants, only to find they never existed.
The centre said it is in the process of expanding its premises to handle the demand for care in the region.
Lancashire police confirmed it was investigating allegations involving an ex-employee of the centre.
Alison Shorrock, centre manager, said the staff and people who used the facilities had been left "devastated" by the news.
"I was shocked as we thought the remaining grants were in place, but as we rang them one by one, to our absolute horror, we found out that there was absolutely no funding still to come. They had never heard of us.
"We were running around like children at Christmas because we were so excited at the possibilities that the new centre would bring for all the disabled people, and suddenly to have your hopes and dreams crash to the floor was one of the worst moments of my life."
The centre, on Pedders Lane, now say they need to raise Â£500,000 to pay off their immediate debtors, including those involved in building an extension to the building.
About 200 groups a month use the centre's facilities, which include multi-sensory areas.
It opened in 1993, with the company securing the building next door in 2011 to expand and build a further sensory room, due to open shortly.
A Lancashire Police spokesperson said: "We have been made aware of a report regarding financial irregularities made in relation to an ex-employee and inquiries are ongoing to establish the full facts."
A Lancashire centre which provides services for disabled people faces possible closure after allegations of "financial irregularities".