Great Western Railway and London North Eastern Railway services have been suspended over fears of cracks in carriages, with passengers urged not to travel.
Urgent inspections are being carried out in more than 1,000 trains across the two operators’ fleets, after hairline cracks were discovered in several of its high-speed trains.
A spokesman for GWR said the cracks were found in two of its Hitachi 800 trains during routine maintenance, and that all trains of this model now had to be inspected.
He added that LNER, which operates the East Coast Mainline, was facing similar problems.
Customers are advised not to travel on Saturday as all high-speed GWR services between London, Bristol, Cardiff and Penzance have been cancelled.
LNER is also advising its customers not to attempt to travel.
A GWR statement said: “Due to some of our Intercity Express Trains being withdrawn from service for precautionary checks, there will be network wide disruption to services today. Please check before you travel.”
LNER said: “We are experiencing significant disruption. Please do not travel today. Your tickets will be valid up to and including Sunday 16 May 2021 (a new reservation must be made).
“If you choose not to travel at all, you can claim a refund from your point of purchase.”