On Monday, the Criminal Bar Association, which represents senior lawyers in England and Wales, voted to strike from next week in a row over legal aid funding.
Justice minister James Cartlidge called the walk-out "disappointing", as the court system battles significant backlogs in cases.
Four weeks of action begin on Monday and Tuesday, increasing by one day each week until a five-day strike from July 18.
Teaching staff and workers in the state-run National Health Service are reportedly also mulling strike action.
And several other transport unions are balloting members over possible strike action, which could go ahead in the coming weeks.
'RUTHLESS'
Transport Secretary Grant Shapps said the disruption would cause "misery" and force hospital patients to cancel appointments.
Pupils sitting exams -- including his own children -- would face extra pressures through having to change their travel plans, he said.
"The RMT is punishing millions of innocent people, instead of calmly discussing the sensible and necessary reforms we need to make in order to protect our rail network," he added.
The government is under pressure to tackle inflation and rising household bills that have left many Britons struggling to make ends meet.
But Treasury minister Simon Clarke ruled out "inflation-busting pay increases" in the public sector to avoid fuelling inflation further.
The government and rail operators maintain that modernising the network is necessary as travel use changes, particularly after the pandemic.
But unions, including the RMT, say profit is being prioritised over pay, pensions and passengers, and that cuts put safety at risk.
"If there's not a settlement, we will continue our campaign," Lynch told Sky News on Sunday.
The government was being "just as ruthless as P&O but they haven't got agency workers to step in", he added, referring to the mass sacking of staff at the ferry operator earlier this year.
