The rail strikes dispute will be "indefinite" unless the Government stops "blocking" a deal being reached, Mick Lynch warned tonight.
The General Secretary of the RMT also accused the Tories of attempting to paint organised workers as the "enemy of this country".
It comes as the country braces for another wave of rail strikes in the build-up to Christmas with widespread disruption starting next week.
Hopes of securing a deal crashed on Sunday after an offer from the Rail Delivery Group of an 8% pay rise over two years was rejected.
The RMT boss accused ministers of inserting the controversial issue of driver-only trains into the negotiations on Sunday - scuppering any chance of a deal.
Speaking at the RMT offices in London last night, Mr Lynch said the union will "go down on this issue" and will not accept driver-only trains "in any form".
Asked whether the dispute could continue indefinitely unless the Government backs down, he replied: "It will be indefinite if that's their position."
"I can't change that. The only people who change that is the National Executive [of the RMT].
"But they are bound by a decision of our annual general meeting that is the policy of the union: we will not accept driver-only operation."
He added: "In my view they are deliberately doing this because they want the industrial action.
"They want this image going on over Christmas that somehow organised working people are the enemy of this country"
On Wednesday the Transport Secretary Mark Harper repeatedly dodged questions on whether the issue had been inserted into the negotiations at the eleventh-hour by ministers.
Speaking at the Treasury Committee, he claimed: "No-one is trying to stop a deal - quite the reverse.
"We're trying to reach a deal here, it's the RMT that has rejected, and I think it's regrettable. I'm very clear I want to see a deal reached."
But Mr Lynch added: "There is no prospect of settling this dispute. There was a prospect of it at the weekend. We're blocked by this Government."
It came as Labour vowed to fight Tory plans to limit paramedic and firefighter strikes "every step of the way" today.
Shadow Chancellor Rachel Reeves vowed to oppose the "grandstanding" threat from Rishi Sunak to impose minimum service levels on 999 staff.
But she declined to say if she would give nurses a penny more than the Tories’ 4.75% pay offer, saying: "Labour will not pluck numbers out of the air."
She admitted “I totally understand why workers are looking for a pay rise”, but pinned the blame squarely on the Tory government.
“The reason we didn’t have strikes under the last Labour government was the last Labour government treated key workers with respect and got round the negotiating table,” she said.
“This government has been sitting on its hands for the last five months."
The government’s own officials believe minimum service levels could trigger even more strikes, it emerged tonight.
A Department for Transport impact assessment warned the crackdown on the railways could have a “significant unintended consequence”.
This could include more staff working strict hours in action short of a strike, which could have a “significant negative impact” on the number of train services, it warned.
“A similar risk is an increased frequency of strikes following a Minimum Service Level being agreed,” said the bombshell document - placed online quietly in October and highlighted by i News.
“Although service levels would likely be higher than the baseline, it could mean that an increased number of strikes could ultimately result in more adverse impacts in the long term.”
The document also warned restricting unions “could result in lower pay and conditions” for workers, high costs and “many months of protracted legal disputes”.
