Welsh Conservative councillors in Powys have written an open letter to the council leader, demanding urgent intervention over what they describe as “wholly unacceptable” failures in waste and recycling collections.

The group says it has “lost all confidence” in the cabinet member responsible for the service and the wider cabinet, following weeks of disruption after new collection routes were introduced in March.

In the letter, the Conservative group claims some households have gone up to five weeks without collections, while others have experienced “irregular and unpredictable pickups”.

They say councillors across the county have been “swamped” with complaints from residents about missed collections.

“The reality for many residents across Powys is now wholly unacceptable,” the letter states.

It adds that the problems can no longer be dismissed as “teething issues”, arguing the council is failing to meet its statutory duty to provide an effective waste and recycling service. The group also criticises communication with residents, saying updates have been inconsistent, unclear and sometimes issued late, leaving people unsure when their waste will be collected.

The group has called on the Liberal Democrat-led administration to intervene directly, review the new system, and issue a public apology to residents.

They have also urged the leader to consider calling an extraordinary meeting of the full council to discuss the issue.

The criticism follows a county-wide change to collection days, introduced as part of a wider review aimed at improving efficiency across Powys, which covers more than 69,000 properties over 2,000 square miles.

Responding to the concerns, a spokesperson for Powys County Council said disruption had been anticipated due to the scale of the changes.

The spokesperson said: “There have been issues with the new collection rounds which was to be expected from such a large scale change to all the routes. We have been honest in our publicity that we did expect some initial issues and have asked that residents do bear with us whilst the routes settle down. Crews will not be used to these routes which does mean that in some instances it will take some time until they are able to complete them within the working day. There will also be more missed properties to begin with due to unfamiliarity with the rounds. Whilst extensive modelling has taken place, it is not possible to try out new rounds in a real world situation until they are actually implemented. We are continually reviewing the new routes and will make adjustments as required.

“In most cases the collections are being completed in the following days so that residents do not have to wait too long between collections. Unfortunately, routes do need to be optimised periodically due to changes in the composition of waste and recycling, additional properties, updates to collection vehicles, and changes in bulking locations. This is common to all local authorities and there will always be some issues when this happens. We do understand that this is an inconvenience for residents and apologise for this. We are working very hard to resolve all the issues as quickly as possible, but do ask for patience as we go through this process. In the meantime we would ask that residents check the bin collection day facility on our website which is kept up to date daily with any changes to collections.”