A law on how trade unions operate in Welsh public services will be scrapped in Westminster under plans published on Monday.
It could mean agency staff are able to replace public sector workers who go on strike.
UK government published the plans after last week's rail strike a move one union called "cynical".
The Welsh government said it would "resist" attempts to undermine legislation passed by the Senedd.
The UK government said it would lift the ban on agency workers and overturn a law passed by the Senedd, five years ago, to make sure the ban disappears in Wales too.
The move is likely to anger Welsh Labour ministers who hailed the Trade Union Wales Act in 2017 as a way to protect the rights of unions in devolved public sectors, such as health, education and councils.
The act stops the use of agency workers during strike action in those services.
It also applies to the rail company Transport for Wales, which is wholly owned by the Welsh Government.
Ministers in London have decided to change the law so employment businesses can supply temporary agency workers to cover for strikes.
Because the 2017 Welsh act prohibits the use of agency workers in such a way, as it stands the regulations will not apply to devolved public bodies.
As a result, the UK government said it "intends to legislate to remove the Trade Union (Wales) Act 2017 through primary legislation when Parliamentary time allows, to ensure trade union legislation applies equally across Great Britain".
Since the 2017 Act, changes to the Senedd's powers have made clear that industrial relation are a "reserved" matter, meaning that they are decided in Westminster not Cardiff Bay.
The GMB union pledged to fight the UK government's plans.
"Let's be clear on this, the UK government has no right to get involved here - they are overstepping the mark," said Tom Hoyles, the GMB's political officer for Wales.
"Their vindictive trade union bill was overturned in Wales six years ago," he added. "This is a clear attempt to create division and divert attention away from their internal party chaos and failure to tackle the cost of living crisis.
"They should butt out."
The 2017 Act also overturned a 40% support threshold for strike ballots, restrictions affecting time off for union activities and the taking of union subscriptions directly from pay packets.
The UK government says scrapping the ban on agency staff, which needs to be approved by the UK Parliament, would limit the impact of strikes. Opponents say it would undermine pay and conditions.
A Welsh government spokesperson said: "Imposing tighter restrictions on trade unions and further reducing the rights of people at work is counter-productive and against everything we stand for in Wales. The UK government's plans will do nothing to improve the lives of working people."
"We will resist any attempts by the UK government to undermine both how devolved public services operate and legislation which has been passed by the Senedd."