All London Underground and Overground train lines were suspended or part suspended on Friday and dozens of bus routes in the west of the city were disrupted, Transport for London (TfL) said.
Tens of thousands of workers from the wider national rail network walked out on Thursday and will do so again on Saturday.
Commuters across the country have already endured disruption from rail strikes this year, organised by unions demanding pay and conditions for their members that better reflect the soaring cost of living caused by energy price-driven inflation.
Data showed inflation at 10.1 per cent in July, the highest since February 1982, as rising energy costs resulting from Russia's invasion of Ukraine hit consumers directly through their household bills, and indirectly through rising food prices.
That has led to a stand-off between firms, who say rising costs and falling demand limit their room to negotiate, unions who say their workers cannot afford to live and the government, which is worried that big wage increases may fuel inflation.
"We don't want to be in a 1970s vicious circle where you end up with salaries increasing, inflation increasing and so on and so forth. You never get out of this," Transport Secretary Grant Shapps told the BBC.
The RMT said the underground strike was in response to a lack of assurances about jobs and pensions from TfL. In a letter to Shapps, the union accused him of waging ideological war against rail workers.
TfL is itself in prolonged negotiations with the government after the expiration of an emergency state funding deal, in part necessitated by a post-pandemic fall in passengers.
Workers in other British industries are also planning future strikes or moving towards industrial action, including port workers, lawyers, teachers, nurses, firefighters, and waste collection, airport and postal staff.Â
