The introduction of a new 12-sided £1 coin to counter international forgers could end up costing local authorities in Sussex hundreds of thousands of pounds.

Chancellor George Osborne’s pre-budget announcement to introduce the new coin by 2017 followed moves by a Dutch smuggling ring to flood the UK with £30 million in fake currency.

But the new coin will mean councils will have to recalibrate hundreds of parking meters across the county to accept the new currency.

The introduction of new 5p and 10p coins back in 2012 forced councils to make similar changes – and almost ended up costing Brighton and Hove City Council £350,000.

That’s how much the authority was quoted for the contract to change the city’s then 1,100 parking machines which the authority say now would have been paid for by motorists.

But instead of paying to adjust the machines, the council was able to adjust tariffs by rounding the tariff either up or down to minimise the use of the smaller coins and avoid the extra cost.

Councils admit they won’t know the full costs until more details of the new coins are released.

The new £1 coin will be similar to the existing £2 coin which has both gold and silver-coloured metals making it harder to counterfeit.

It is the same shape as the 12-sided threepenny or ‘thrupenny’ bit which was in circulation from 1937 until decimalisation in 1971.

A Brighton and Hove City Council spokesman said: “It’s too early to say because the exact composition of the coin is not yet known and, until it is, the company manufacturing the coin selectors won’t have manufactured the piece of kit needed.

“The other key factor is this change isn’t due until 2017 and with the full roll out of PaybyPhone due to be completed in May this year – which will include the ability to pay at PayPoint sites in shops around the city – it’s likely the number of machines on street will have been reduced.”

The spokesman added that motorists could avoid the issue of change altogether by paying for parking by mobile phone which since its introduction in September now accounts for around one in 11 of all transactions.

An East Sussex County Council spokeswoman said: “Until we have full details of the new coin, we will not know what changes are needed to our 350 parking machines.

“Changes to parking machines following the introduction of the new 10p and 5p coins two years ago cost the county council about £30,000.”

A West Sussex County Council spokesman said: “There will be a cost to upgrade the coin mechanisms to accept the new pound coin if and when the change happens.

“The older machines will be more expensive to upgrade than the newer ones but we will not be able to estimate a cost until the machine manufacturers have had a chance to test the new coinage.”