The National Education Union (NEU) said it is prepared to ballot its 450,000 members if an increase in pay more in line with inflation is not offered.
NASUWT leaders have also called for a 12% pay increase for teachers this year and said it will ballot members in England, Wales and Scotland for industrial action if its demands are not met.
A pay award for 2022/23 is due in November.
Why are teachers threatening to strike?
The NASUWT, a TUC-affiliated trade union which represents teachers in the UK, said two in three teachers are questioning whether to change careers due to wages after the value of teacher’s pay has dropped by 20%.
Dr Patrick Roach, NASUWT general secretary, said: “Teachers are suffering, not only from the cost-of-living crisis, which the whole country is grappling with, but 12 years of real terms pay cuts which has left a 20% shortfall in the value of their salaries.
“If the government and the pay review body reject a positive programme of restorative pay awards for teachers, then we will be asking our members whether they are prepared to take national industrial action in response.
“The government wrongly assumed teachers would simply stand by as they erode pay and strip our education system to the bone.
“But this weekend, thousands of teachers, from every corner of the UK, joined together to demonstrate our strength, unity and determination to stand up and to fight back.
“Our message is clear and has now been delivered directly to the government on their doorstep. We will not allow cuts to our members’ pay and attacks on their pensions.
“If a pay rise is not awarded, it will be won by our members in workplaces through industrial action.”
The NASUWT was a prominent group in a large rally on Saturday, organised by the Trades Union Congress (TUC), which saw thousands of protesters march through central London to demand better pay and working conditions.
If a pay rise more in line with inflation is not offered, the NEU said a letter will be sent to Education Secretary Nadhim Zahawi on Wednesday (22 June) saying the union is prepared to ballot its members.
Dr Mary Bousted, fellow joint general secretary of the NEU, said: “The case for a better deal for teachers will be set out in full this Wednesday in our letter to the Secretary of State.
“If it should fall on deaf ears, and teachers are offered a pay rise significantly below inflation, then we will proceed to an indicative ballot of our members.
“Teachers have had enough of a government which simply does not value them. The combination of unsustainable hours, the work intensity during those hours and ever-falling pay levels are damaging for our schools and the young people we are educating.
“The government has so far been unwilling to acknowledge and properly remunerate the work that teachers do.
“Teacher pay has fallen by a fifth in real terms since 2010. We need a pay deal for all teachers which recognises this reality.”
Could nurses also strike?
Unison has warned industrial action could also spread to hospitals unless a pay deal close to inflation is agreed.
Christina McAnea, Unison general secretary said: “The government has a simple choice, either it makes a sensible pay award, investing in staff and services and reducing delays for patients, or it risks a potential dispute, growing workforce shortages and increased suffering for the sick.”
Chairman of the NHS Confederation Victor Adebowale warned a real-terms pay rise for the lowest paid NHS staff was needed to avoid “a worsening of the NHS workforce crisis”.
Shadow Levelling Up Secretary Lisa Nandy has called on Tory ministers to “listen seriously” to workers’ concerns.
She said: “It’s not about whether workers go on strike, it’s about the fact we have a government that’s currently on strike and not doing its job.
“This is a government that in 2019 came to power on a promise to level up and instead what they’ve presided over is absolute chaos.
"Chaos at the ports, chaos on the railways, chaos at airports, chaos everywhere you go, and that is because this is a government that is not doing its job.”
Biggest rail strike in 30 years from Tuesday
The threat over industrial action comes as rail services across the UK and on the London Underground will grind to a halt from Tuesday (21 June) in the biggest walkout in the industry for more than 30 years in a row over pay, jobs and conditions.
Members of the Rail, Maritime and Transport union (RMT) at Network Rail (NR) and 13 train operators will strike on Tuesday, Thursday and Saturday, with only around one in five trains running and disruption to services on days following the action.
The RMT and Unite is also holding a 24-hour walkout on London Underground which will cause huge disruption to the Tube.
The TUC is calling on the Westminster government to adopt a positive role in the dispute, saying it was “inflaming tensions” with comments such as threatening to “revoke” workers’ legal rights.
The union organisation said rail workers in Wales have reached agreements with rail operators on pay and job protections while in Scotland there are “meaningful negotiations” taking place.
The TUC said ministers in Westminster were insisting on imposing cuts and planning to change the law so that employers can draft in agency workers in during industrial action, which it added was reminiscent of the action recently taken by P&O.
TUC general secretary Frances O’Grady said: “The government has the power to help end this dispute but rather than working in good faith to find a negotiated settlement, ministers are inflaming tensions and trying to pitch worker against worker.
“Instead of threatening to do a P&O on these workers and rip up their rights, ministers should be getting people around the table to help agree a fair deal.”
A Department for Transport spokesperson said: “Strikes should always be the last resort, not the first, so it is hugely disappointing and premature that the RMT is going ahead with industrial action.
“The government committed £16 billion – or £600 per household – to keep our railways running throughout the pandemic while ensuring not a single worker lost their job.
“The railway is still on life support, with passenger numbers 25% down and anything that drives away even more of them risks killing services and jobs.
“Train travel for millions more people is now a choice, not a necessity. Strikes stop our customers choosing rail and they might never return.”