Members of the first fire crews to attend Grenfell Tower have expressed frustration at the time it took to send backup engines, a delay that hampered their ability to evacuate more people, the head of the firefighters’ union FBU has said. General secretary Matt Wrack, who has spoken to firefighters who attended the blaze, said the delay may have been worsened by closures of local fire stations.

He said some of the firefighters had asked the union to highlight concerns about the time they had to wait for the second wave of firefighters during the crucial early stages, as they struggled to evacuate residents. Cuts to firefighter numbers and a process of fire safety deregulation should be a key part of the public inquiry into the disaster, Wrack told the Guardian.

But he said the initial list of questions the government-commissioned inquiry sets out to answer did not explicitly address either issue. Wrack said his union would boycott the whole inquiry if members felt these crucial issues were not being addressed. “There have been fire station closures and fire engines axed,” he said. “Some firefighters who were there have said to me that a quicker response earlier might have made a difference.” A long-term deregulation of fire services and safety rules should be scrutinised, Wrack said. “David Cameron described health and safety as a monster. He discussed an over-obsession with health and safety in the fire service. He should answer some questions,” he said. Firefighters wanted senior figures to be held accountable, he added, and would not be satisfied with a prosecution of a “subcontractor who screwed a bit of cladding to the building”.

The union leader concluded: “If regulations affected this, who signed the regulations? If policies were adopted who adopted the policies? This was the worst fire since the Blitz in terms of loss of life. If political decisions have helped lead to that outcome, the ministers responsible should be gone.”