Firefighters who tackled the Grenfell Tower inferno say they have never experienced a blaze like it in decades of service.

As funding pressures on emergency services remain sharply in focus – particularly in light of the Metropolitan police commissioner, Cressida Dick, saying she would be seeking more resources for her force following the London Bridge attacks – the fire service has risen to the challenge against a background of cuts.

A total of 200 firefighters and officers fought the blaze, arriving in 40 fire engines with the first on the scene just six minutes after receiving the first call at 00:56.

On the ground, feedback on resources from firefighters – some of whom are approaching 24-hour shifts – has been mixed, with some expressing frustration and others believing they were adequately equipped.

A London fire brigade firefighter of 17 years, who asked not to be named, said he had never seen or dealt with anything like the blaze at Grenfell Tower.

Working from a command unit on Ladbroke Grove, he said he had been on the 12th floor and it had been “devastating”. Firefighters had to access the building using specialist breathing apparatus, he said.

He began his shift at 8pm on Tuesday, arrived on the scene at 4am and was due to start his next shift at 8pm. “Everyone has been going above and beyond,” he said. “Many of the men have been lining up to work today and assist.”

He said the brigade was now testing the “integrity” of the building. “Parts of it are OK,” he said.

Flames and smoke engulf Grenfell Tower. Photograph: Adrian Dennis/AFP/Getty Images

He said he was happy with resources and believed they were sufficient. One fireman said he had never seen a fire like it. “And I hope I never do again,” he said. “It would be unlucky to see this twice. It was surreal.”

Other firefighters said they could not speak freely, but had been in the fire, rescuing residents. Some had used up four oxygen canisters going in and out of the flames. Cuts to the fire service had taken a serious toll on operations, they said.

“Put it this way, you’re meant to work on a fire for a maximum of four hours, we’ve been here for 12. Hopefully, we’ll get home at some point before we have to come back tonight.”

Speaking at the scene the London fire brigade commissioner, Dany Cotton, said: “This is an unprecedented situation, with a major fire that has affected all floors of this 24-storey building, from the second floor up.

“Over 200 firefighters and officers are attending this incident, with 40 fire engines and a range of other specialist vehicles, including 14 fire rescue units in attendance.”

Cotton, who became the first female commissioner of the London fire brigade earlier this year, added: “Based on the level of resources that were needed at this fire we declared it a major incident in the early hours of this morning.

“London fire brigade’s control room took multiple calls, with the first being received at 00.54am. The first fire crews were on site in under six minutes.

“Crews wearing breathing apparatus have been working in extremely difficult conditions to rescue people and bring this major fire under control.

“The cause of the fire is not known at this stage and, clearly, we will be here all day and will be providing further updates, working with the police and ambulance service.”