Budget proposals for the new Dorset Council include a £3.1m ‘adjustment’ because of assumptions that the new authority will get less than it would like from Government settlements and other income streams.

The new authority is expected to start its first financial year in 2019 with a £15.4 million budget shortfall, according to the most recent calculations.

Finance brief holder Cllr Tony Ferrari told the Dorset Council shadow executive at a meeting in Dorchester that there are were still several areas where the final sums would not be known until shortly before the new council comes into being next April.

He said that to help the process an assumption had been made about income and £3 million had been included in the budget projection to cover some of the unknown items – but he said that even this could be increased by taking money from other areas, should the need arise.

“I am confident we have adequate reserves if we need to short-term fund…it’s not easy when so much is unknown but I think we have a sensible budget proposal,” he said.

In response to a later question he admitted that even the ‘convergence’ savings from bringing the councils together could not yet be accurately calculated until the shape of the new council had been agreed. It is only then that the number of staff needed can be calculated and, by default, how many job losses there will be.

At the moment the new council does not know if there will be a cap on the level of council tax it can levy, or whether the level of council tax can be harmonised across the county. It is also uncertain about how income from business rates can be used and whether or not it can increase fees and charges.

Last week Dorset County Council Liberal Democrat leader Cllr Nick Ireland said that he now doubted if the move to a unitary council would save any money although a recent projection from the shadow authority does predict savings by 2020-2021, achieved mainly through job losses.

Other doubts exists over whether the council has enough staff at its disposal to carry the change programme through which, in turn, could lead to extra costs.

The cost of change was put, at the meeting, by Cllr Peter Wharf, at between £25 and £35 million.

One of the key risk areas identified in a report to the committee concludes: “Resource required to deliver the phase 3 plan will greatly exceed that within the current programme: this requirement will need to be resourced.”

When asked what this meant the officer heading the change programme, Keith Cheeseman, said that it could mean taking on more temporary staff and consultants to help the change process through, but that requirement could not yet be calculated.