Wiltshire Police is expected to spend more than £10 million (€11.1m) dealing with the Novichok poisonings.
Officers from 40 other forces were called in after two major incidents were declared in Salisbury and Amesbury in the space of four months.
It is estimated that the cost of bringing in officers from other forces will be more than £7 million (€7.8m), with more than £1.3 million (€1.4m) being spent on overtime within Wiltshire Police.
This was to ensure that officer numbers could be maintained across the area while dealing with the attacks.
The total also includes £347,000 (€385,775) spent on destroying a number of police vehicles, which had to be disposed of as a precaution.
Police and Crime Commissioner for Wiltshire and Swindon Angus Macpherson has said that he “fully expects” the Government to cover the bill.
Wiltshire Police had to cancel officer rest days and put annual leave requests on hold to deal with the incidents and also brought in private security to guard cordons.
“Our mutual aid arrangements mean that other front line policing duties have remained unaffected in Wiltshire despite us dealing with two internationally significant incidents in just four months.
“I am assured that the Commissioner will continue his dialogue with the Government to ensure that Wiltshire Police and the communities we serve are unaffected by these growing costs,” Chief Constable Kier Pritchard said.
Mutual aid is a resource that is used when the scale of an incident creates additional pressures and need for support.
The £10 million (€11.1m) total does not include the cost of the Metropolitan Police’s investigations.
Ex Russian spy Sergei Skripal and his daughter Yulia were attacked with a military-grade Novichok in Salisbury in March.