All train companies will have to join a new rail ombudsman scheme being launched to handle complaints from passengers, the Office of Rail and Road (ORR) has announced.
The licences of rail operators will be modified so they will not be able to decide whether or not to join or leave the scheme, which is expected to begin later in the year.
The ORR said the change was necessary to assure passengers that complaints will always have independent scrutiny.
The ombudsman will be "free and independent" and able to make decisions which are binding on rail companies.
ORR deputy director of consumers, Stephanie Tobyn, said: "Our surveys show that passengers are often dissatisfied with the way their complaints are handled, and this damages their trust in rail companies and the railway industry in general.
"An ombudsman scheme will give passengers real certainty, consistency and clarity in how their complaints are handled; that is why we want every rail company to be required to join it."
A spokesman for the Rail Delivery Group said: "The Rail Delivery Group and train companies committed last year to introducing a new independent ombudsman to investigate and rule on unresolved customer complaints.
"The partnership railway, in its recently published long-term plan, has committed to increase customer satisfaction by improving the railway to remain the top-rated major railway in Europe.
"The creation of a new ombudsman, supported by the industry, will help build confidence in our services and we are pleased that the rail regulator supports this."
Anthony Smith, chief executive of the independent watchdog Transport Focus, said: "Passengers will welcome the consistency that comes with all train companies becoming members of the new rail ombudsman scheme.
"The rail network needs to work as just that with no gaps in consumer protection coverage."