LONDON, June 21 (Xinhua) -- After last-ditch talks between unions and rail operators broke down here on Monday, the United Kingdom's (UK) National Union of Rail, Maritime and Transport Workers (RMT) gave the go-ahead on Tuesday to the country's biggest rail strikes in 30 years that are expected to cause massive disruptions to rail services in England, Scotland and Wales.

Only about 20 percent of passenger trains were scheduled to run after staff walked off the job at 12 midnight on Tuesday. The walkouts will continue on Thursday and Saturday this week, affecting millions of passengers.

More than 40,000 RMT union members, including guards, catering staff, signalers and track maintenance workers take part in the labor action.

The RMT is in a dispute with the rail operators over pay, pensions and job cuts. People across the UK are struggling with rising living costs and seeing their salaries eaten up by inflation. In April, UK inflation soared to 9 percent, and the Bank of England projected a figure exceeding 10 percent for the end of this year.

Meanwhile, UK rail companies are set to cut jobs, pay and pensions as rail passenger numbers have not returned to pre-COVID-19 pandemic levels.

"The British worker needs a pay rise," RMT Secretary General Mick Lynch said. "They need job security, decent conditions and a square deal in general. If we can get that we won't have to have the disruption in the British economy that we've got now and which may develop across the summer."

Andrew Haines, chief executive of UK operator Network Rail, said he was "profoundly sorry" to passengers for the disruption but blamed the RMT for not willing to compromise.

The Conservatives-led UK government said it was up to the unions and employers to negotiate pay and conditions, while the opposition Labour Party and the unions believed Transport Secretary Grant Shapps should be involved in the talks.

UK Prime Minister Boris Johnson urged "the union barons to sit down with Network Rail and the train companies" to negotiate a deal.

A separate strike also took place on the London Underground on Tuesday. There are warnings this could be just the start of a summer of strikes, with teachers and nurses also threatening industrial action out of similar grievances.

National Highways, which operates and maintains strategic road networks, advised on Tuesday that the country's motorways and major A-roads are expected to be busier than usual in the coming days.