Just one in seven of Belfast Bikes still on road due to vandalism
Fewer than one in seven Belfast Bikes are now in operation amid a growing wave of vandalism.
Under 80 of the public hire bicycles are currently available out of nearly 600.
It is believed that number has dropped even lower at times.
Police have made a raft of arrests in relation to attacks on the bikes.
A serious spike in vandalism and theft over Halloween "affected the fleet dramatically", Belfast Bikes said.
As a result there were only 128 operating at the end of October. More than 70 were targeted in the space of just three days, and the problem is understood to have gotten worse.
The operators added: "It is a challenge dealing with the high levels of theft and vandalism, but we are working extremely hard to combat this.
"Vandalism and anti-social behaviour are the causes, with vandalism increasing over Halloween.
"PSNI and Harbour Police have made a significant number of arrests and are following further significant lines of enquiry for other incidents.
"We are all working with elected representatives and relevant agencies, including the youth justice agency, to address the levels of anti-social behaviour.
"We are also working hard on community engagement plans and we are now working with some of the youths arrested previously on an education/work experience programme which is in the early/trial stages."
It said that due to a new delivery of parts, bike numbers should "increase rapidly day-on-day and increase the number of bikes available substantially".
It emerged earlier this year that 210 of the 576 Belfast Bikes had either been stolen or taken out of service due to vandalism, costing almost £1,800 per month.
But the problem has worsened since then.
The scheme has surpassed 552,000 rentals in 948 days, and averaged around 500 rentals daily in October and last month.
There are around 40 docking stations across the city.
Earlier this year the scheme announced it was moving and setting up new stations in areas such as Ormeau Road and Stranmillis.
Users pay a yearly subscription of £20 and get the first 30 minutes of their daily journey free of charge, before paying a small fee for each hour.
The scheme said repairs and works were ongoing and numbers fluctuate on many factors, predominantly anti-social behaviour, "which we are all addressing on all fronts".
"Parts have been dispatched by Nextbike to enable us to carry out the necessary repairs," it added.