Four Kent councils have confirmed they are to move ahead with a merger plan under what has been hailed as one of the biggest shake-ups in local government in recent years.

Those involved say it is the only way forward and would help improve services and save taxpayers money.

But at a press briefing at Dover District Council to announce the proposed merger there was a suggestion council tax bills for some in the new combined authority could increase.

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Leaders said there would be winners and losers under different scenarios.

One calculation suggests that if councils were to raise the equivalent money they currently do when a new merged council is formed bills in Dover may increase by 19.9% while in Canterbury the increase would be 7%.

However, under a different scenario, there would be more modest changes.

One calculation based on how much council's currently raise through the council tax suggests bills in Canterbury might increase by 3.2%, while Dover taxpayers could pay 5.5% more.

Shepway would see a decrease of 0.3% and Thanet a 1.2% increase.

Under the proposal could be an estimated 8% cut in the 1,850 strong workforce across Thanet, Shepway Dover, and Canterbury. Of these, about half would be the most senior staff.

However, council leaders insisted staff cuts would be more severe among senior managers as the proposal would involve a single management team running the new authority.

There would also be a cut in the number of councillors serving on the new authority with consultants who produced the business case suggesting that between 70 and 100 elected members could be removed from the overall total.

But Ashford council said it had decided not to join up. Leader Gerry Clarkson said: “However having received the business case we do not believe it is in the best interest for our borough or represents value for money for our residents. We also feel it is not in the best interests of the other four authorities for us to continue either.”

On the financial side there could be savings of £6.8m in the first two years and £6.4m each year thereafter compared to the individual councils’ current budgets.

Councillor Chris Wells the leader of Thanet council said the four authorities would have to deal with £60m less in the next few years under the government's austerity drive and that merger would help save an estimated £40m.

“The business case clearly identifies the creation of a single East Kent council is an ambitious but logical step for councils.

“With greater scale and resources it could transform services at a higher quality and lower costs two residents and strengthen our position economically,” he said.

Cllr Simon Cook, the leader of Canterbury City Council said: “It is incredibly ambitious.

“This is the first time that four councils in the country have come together to form one single council.

“It will be a complicated task but it is definitely one worth considering.”

“There are some real great opportunities for us.

“East Kent is an economy in itself and fitting one council across the economy could work fantastically well.

“We would have one strong voice to talk for the East Kent economy.”

The business case says the costs of setting up the new merged council could be as much as £225,000.

Ashford council has confirmed it is not going to be part of the super-council, but it is committed to working closely with the new authority.

• Here's a look at our live blog as the announcement was made.

[Live Grid - Supercouncil]