Belfast City Council is considering legal action against a distribution company after nearly half the letters it was supposed to deliver - informing ratepayers of new bin collections - were apparently dumped in a skip.
The council has apologised after up to 40% of Belfast residents did not receive notification of the changes. Hundreds of the letters were "found dumped in a skip", the council revealed yesterday.
In a major re-organisation, bin collection day has changed for around 160,000 households on 310 routes across Belfast.
It is understood that the council is considering legal action over the matter.
Director of city and neighbourhood services for the council, Nigel Grimshaw, said a contractor had "let them down" and human error was to blame.
He told BBC Radio Ulster's Nolan programme that extra resources had been directed to resolving the confusion.
"I need to apologise to the residents of Belfast... the level of disruption has been much more significant than anticipated," he added. "We were dealing with a contractor and, unfortunately, the contractor let us down on this occasion.
"Ultimately, we can have our conversation with the contractor, but at the end of the day, residents rightly expect the council to deal with this matter, and that's what we're doing.
"We are working very hard at the minute to prioritise everything around this to ensure that we put a fix in place that resolves these issues for people as quickly as possible."
In a statement, the council said: "There were 160,000 letters produced, covering 310 different bin routes. This was a very complex operation, and it was supported with social media, press and online coverage.
"However, as the new bin collections began to take place, we realised that our communications did not seem to have reached many residents and, upon investigation, we discovered that approximately 30-40% of the letters not delivered on the first day. We were also advised yesterday that letters were found in a skip in the Oldpark area. When this was inspected, we retrieved hundreds of letters."
Council workers are now working overtime, with extra squads deployed to deal with any bins due to be collected under the new regime.
New collection days can be checked at www.belfastcity.gov.uk/bins