The Tories are expected to announce on Sunday that they will bring in new laws to outlaw some rail strikes.
The Conservative manifesto on Sunday may set out plans to legislate for some services to run during industrial action.
The move comes ahead of 27 days of strikes during December on South Western Railway by members of the RMT union over guards on trains. West Midlands Trains workers were on strike on Saturday over the same issue.
RMT general secretary Mick Cash said, "Banning strikes is the hallmark of the right wing junta, not a democratically elected British government.
"We would fight any attempt to strip our members of their basic human rights.
"What the Tories are after is banning rail workers from striking to defend passenger safety and accessibility and that is a disgrace.
"This is old school class war from the Tories and would give the green light to the greedy private train companies to unleash havoc completely unchecked in the pursuit of profits."
Mick Whelan, general secretary of the train drivers' union Aslef, said, "The right to strike is a fundamental human right. We are not slaves.
"Johnson only acts on behalf of the boss class in Britain."
TUC union federation general secretary Frances O'Grady said, "The Conservatives want to make it harder for workers to stand up for decent services and safety at work, and to defend their jobs and pay.”
It is understood that under the Conservative plans, train operators and unions would be required to sign an agreement to run a minimum number of services in the event of strikes.
There are similar laws in France, although they have been defied in recent unofficial strikes.
Such new assaults from the Tories underline that the union leaders have to be prepared to confront the laws designed to strangle a fightback.
It was outrageous that postal workers were prevented from striking after a 97 percent vote for action.
It’s time for the unions to move to serious resistance.
New research this week showed low-income families will be over £500 a year worse off in 2021 than they were in 2010 because of tax and benefit changes.
The TUC said its analysis indicated that the bottom fifth of earners will be £517 poorer within the next two years than they were at the start of the decade, taking into account planned Tory cuts to national insurance.
This contrasts with the top 20 percent of earners who will be £147 a year better off than in 2010, as a result of the government's tax and benefit changes.
Those on average earnings will also lose out, with the typical household £487 a year worse off in 2021 than when the Conservatives came to power, said the TUC.
Its report said that the Conservatives' tax and benefit reforms have "cushioned the blow" of austerity for higher earners while hurting those on lower and middle incomes.
There was a very big anti-Tory turnout at short notice in Sheffield on Friday evening when Boris Johnson and Jeremy Corbyn appeared at BBC's Question Time.
Labour needs to tap into the deep anger against the Tories by holding mass public rallies and unleashing the fury against Johnson. Politeness and manoeuvres will not be enough.