RMT say they will not “hesitate to protest nationally”.
RMT general secretary Eddie Dempsey said: “The UK state pension is already one of the worst in the entire developed world, which is a direct result of decades of governments transferring both our national and personal wealth to the super rich.
“Any decision to squeeze more out of working people by forcing us to work even longer would be a national disgrace.”
Dempsey added that raising the pension age would be a “slap in the face” to taxpaying Brits.
He said: “Raising the pension age even further isn’t just cruel and unnecessary, it’s a slap in the face to the very people who keep this country running.
“If this government makes any move to drastically increase the retirement age, we intend to lead our movement onto the streets and will not hesitate to protest nationally and take coordinated direct action.
“There is plenty of wealth in the economy. The Labour government needs to capture it and distribute it where it is most needed, including funding a decent state pension.”
The Chancellor has said that a review into raising the state pension age is needed to ensure the system is “sustainable and affordable”.
The Government review is due to report in March 2029 and Ms Reeves said it was “right” to look at the age at which people can receive the state pension as life expectancy increases.