Santa Clara County Fire Department is suing Verizon Wireless after the telecoms giant limited firefighters' access as they battled the largest wildfire in Californian state history.

The company throttled the department's service as they were still battling the Mendocino Complex Fire because it had reached its data limit for the month.

When the fire department called Verizon to tell them they were in the middle of dealing with a public emergency and safety issue, a customer service representative told them they should upgrade to a more expensive plan.

In the lawsuit, the fire department says the throttling was a result of the repeal of net neutrality rules.

Before they were repealed by the Federal Communications Commission in December, communications companies were required to provide equal data access to all customers.

County lawyers allege that the slowdown, called 'throttling', was caused by the FCC's action, which allows telecommunications to slow internet speed to selected customers.

The Santa Clara County Fire Department was in the midst of fighting the largest wildfire in California's history when its Verizon 'unlimited' plan's services throttled

When the SCFD contacted Verizon, they were told by the provider they needed to upgrade, despite communicating that they were in the middle of a emergency and public safety issue

The new rules allow companies to limit access to customers who have reached certain data limits.

Despite Santa Clara Fire paying for 'unlimited' data, they were hit with the issue of heavy throttling until they upgraded to a new plan that was more than twice what they were already paying in the middle of a public safety emergency, and despite communicating that with the service provider.

Verizon denies the slowdown was related to the lawsuit or the FCC's repeal of net neutrality rules, which required equal data access to all customers.

However, the firm agreed full service should have been immediately restored to the county when fire department authorities told a customer service representative it was responding to a public emergency, and the department should not have been urged to upgrade instead.

Verizon blamed a communication error and acknowledged the fire department's normal service should have been restored more quickly than it was.

'While Verizon ultimately did lift the throttling, it was only after county fire subscribed to a new, more expensive plan,' Santa Clara County Fire Chief Anthony Bowden wrote in the county's court filing.

Throttling means data was reduced to at least 0.5 per cent of normal speed or less.

'This throttling has had a significant impact on our ability to provide emergency services,' Bowden said in a statement that is part of a lawsuit filed this week in a bid to reinstate federal net neutrality rules.

'Verizon imposed these limitations despite being informed that throttling was actively impeding County Fire's ability to provide crisis-response and essential emergency services,' he added.

Bowden said the incident highlights how crucial, and life saving, reliable service is to ensure emergency responders have access to quick data that could prove lifesaving.

'In large and complex fires, resource allocation requires immediate information,' he wrote.

'Dated or stale information regarding the availability or need for resources can slow response times and render them far less effective. Resources could be deployed to the wrong fire, the wrong part of a fire, or fail to be deployed at all.

'Even small delays in response translate into devastating effects, including loss of property, and, in some cases, loss of life.'

The throttling specifically affected a fire department vehicle 'deployed to large incidents as a command and control resource' and is used to 'track, organize, and prioritize routing of resources from around the state and country to the sites where they are most needed,' Bowden wrote.

On Wednesday Verizon admitted that it had made a mistake in a statement on Wednesday.

'Regardless of the plan emergency responders choose, we have a practice to remove data speed restrictions when contacted in emergency situations,' it said.

'In this situation, we should have lifted the speed restriction when our customer reached out to us.

'This was a customer support mistake. We are reviewing the situation and will fix any issues going forward,' the statement added.

The company added that the incident had nothing to do with net neutrality.

Bowden added: 'In light of our experience, County Fire believes it is likely that Verizon will continue to use the exigent nature of public safety emergencies and catastrophic events to coerce public agencies into higher cost plans ultimately paying significantly more for mission critical service, even if that means risking harm to public safety during negotiations.'

Verizon said the customer service representative should not have forced the fire department to upgrade their services

Internet providers 'have shown every indication that they will prioritize their economic interests, even in situations that implicate public safety,' the lawsuit alleges, according to the filing

The account by Bowden is part of a larger lawsuit, filed by 22 states that are seeking to overturn the government's decision to revoke net neutrality.

The lawsuit argues the FCC failed to analyze how the end of net neutrality would impact public safety.

Internet providers 'have shown every indication that they will prioritize their economic interests, even in situations that implicate public safety,' the lawsuit alleges, according to the filing which was first posted by Ars Technica.

The Mendocino fire which began on July 27 has consumed nearly 407,000 acres, or roughly half the size of Rhode Island, and as of Wednesday it was 74 per cent contained.