The Government’s “unwillingness” to enter into meaningful consultation over single-phrase Ofsted judgments poses “danger” to lives of school leaders, a union has said.

The National Association of Head Teachers (NAHT) should explore “legal and industrial routes” to secure inspection reforms needed to protect staff in schools, delegates at the union’s annual conference said.

An emergency motion on Ofsted, which was unanimously passed at the union’s annual conference in Newport in Wales on Saturday, described the inspection system as “inhumane and unreliable”.

Paul Whiteman, general secretary of the NAHT,  said he put the Government “under notice” over its position on single-phrase Ofsted judgments.

It came after the Department for Education (DfE) last week said it had no plans to remove one-word Ofsted judgments, despite calls for them to be scrapped.

The education watchdog has come under greater scrutiny after the death of headteacher Ruth Perry.

Mrs Perry took her own life after an Ofsted report downgraded her Caversham Primary School in Reading from its highest rating, “outstanding”, to its lowest rating, “inadequate”, over safeguarding concerns.

In its recent response to an Education Select Committee inquiry on Ofsted, the DfE listed benefits of one-word judgments, which included providing a “succinct” summary for parents.

The motion passed on Saturday, which described the DfE’s response as “wholly inadequate”, called on the NAHT’s executive “to explore all campaign, legal and industrial routes” to secure reforms to “safeguard leaders’ lives”.

During the debate, James Hawkins, a deputy headteacher in Birmingham, said: “I have heard colleagues this morning talk about how they have had to retire because it is the only option.

“It is not the only option. The options we have before us as a union is to take action, potentially we could go forward into industrial action.”

He said: “If we don’t stand and rise to this now, colleagues, then we may as well all retire.”

Dave Woods, from the Ealing branch, said: “Single-phrase judgments have no place in our accountability system. They have been proven to be dangerous.

“And if the Secretary of State, Gillian Keegan, is so tin-eared and remains sitting on her posterior then her demise will come.

“Because we will fight and we will continue to fight until such a punitive damaging system is removed.”

Michelle Sheehy, from the Walsall branch, told the conference: “The argument from the Government that parents want single-phrase judgments – well I don’t know who these parents are.”

The motion, passed by delegates, said: “Government’s tin-eared defence of discredited and reductive single-phrase judgments, and its unwillingness to enter into any meaningful consultation or negotiation, poses a real and present danger to the mental health, wellbeing and lives of school leaders and teachers.

“Should another tragedy happen in the future, it will be ministers who need to answer for their decisions.”

Speaking to the media on Saturday, Mr Whiteman said: “Let’s engage with Government and see what they mean by keeping it under constant review.

“And if we don’t get meaningful answers from that, then government is under notice from this conference that I’m now instructed to go and explore what we can do about it.”

He added: “We will take legal advice on the powers of the inspectorate and we will take legal advice on how members protect themselves when they get the call.”

In March, Sir Martyn Oliver, chief inspector of Ofsted, launched the watchdog’s Big Listen public consultation, which closes at the end of this month, to seek views about the inspectorate.

Professor Julia Waters, the sister of Mrs Perry, said: “My family and I are pleased to hear that the NAHT is focused on pushing for all the necessary changes to school inspections, of which single-word judgments are just a part.”

But she added: “I am concerned to see the NAHT using wording that might be seen to suggest that further tragedies such as Ruth’s death would lead to ministers being held accountable. This is dangerous and wrong.

“Every headteacher should know that they can play the best possible role by continuing to work for their pupils and their schools, and to make the case to reform Ofsted by joining together and speaking out.”