Cracks are beginning to show in the collaboration between two east London councils amid a multi-million pound budget gap and an unexpected resignation.

Havering and Newham councils started to work more closely together in 2014 when they created a non-profit organisation called OneSource, which combines the teams responsible for building management, human resources, accounting and legal services.

Eight years later, OneSource is over-budget by £6.4million. Its chief executive Simon Pollock also resigned in December.

A joint committee to oversee OneSource, held on March 11, heard Newham is bringing its workplace investigations service and its health and safety teams back in-house, as it “expects to be able to deliver a more cost-effective and risk-focused service”.

Havering expects Newham to cover the initial extra cost, including an extra £168,000 for its health and safety team - the full cost and reason for Newham withdrawing from shared workplace investigations has not been made public due to “commercial sensitivity”.

At the meeting, the two local authorities disagreed on whether to replace Mr Pollock or leave the post open while the arrangement is reviewed.

Havering Council's leader Damian White said it would be “foolhardy” to delay hiring an interim chief officer during the review.

Newham’s mayor Rokhsana Fiaz disagreed: “What I would suggest is can we find a way of looking at this in the round, given all the various comments we’ve had in this committee, either concerns or happiness about how OneSource is delivering for us.”

The two leaders agreed to delay a full decision on appointing a new chief until after the local elections in May.

In a strategy update for OneSource, assistant director of performance, policy and programmes Liz Carswell said she welcomed having a “relook” at the OneSource model to see “what works and what doesn’t”.

Alongside back-office work for both councils, OneSource also offers services to other local authorities and has its own debt collection operation.

In what Ms Fiaz described as a “cock up” last year, an accounting error led to hundreds of Havering customers being overcharged when two zeros were added to their bills.

Havering Council apologised “unreservedly” for the mistake and said it had cancelled the transactions or refunded the customers, who included market stallholders and parents paying for music tuition.