Virgin Trains is to reverse its decision to stop selling the Daily Mail on its West Coast services.
Virgin Group boss Sir Richard Branson said he instructed the firm to restock the paper while a review takes place.
Virgin Trains had said the decision came after "feedback from our people". But Sir Richard said he was unaware of the move and the operator must never be seen to be "censoring" customers.
The Daily Mail said it welcomed the "support for freedom of speech".
In November, Virgin Trains staff were told in an internal memo "considerable concern" had been raised about the Mail's position on issues such as immigration, LGBT rights and unemployment.
The memo added the paper was "not compatible" with the company's beliefs.
Last week, Virgin said it regularly reviewed its on-board products and it had never sold the newspaper on its East Coast trains, which is under the management of Virgin and Stagecoach.
Virgin West Coast services run between London, the Midlands, the north-west of England and Scotland.
In Sir Richard's statement, he said the chairman of Stagecoach, Sir Brian Souter, was also not aware of the decision.
"Brian and I agree that we must not ever be seen to be censoring what our customers read and influencing their freedom of choice.
"Nor must we be seen to be moralising on behalf of others. Instead we should stand up for the values we hold dear and defend them publicly, as I have done with the Mail on many issues over the years."
Sir Richard added a full review of Virgin Trains' sales policy would be carried out but this should not "single out individual media titles".
Freedom of speech, freedom of choice and tolerance for differing views are the core principles of any free and open society – so we have decided to reconsider our people’s decision over @VirginTrains stocking the Daily Mail https://t.co/hqwPulb2gl pic.twitter.com/Qetcr9rMzp— Richard Branson (@richardbranson) January 15, 2018
A Daily Mail spokesman said it welcomed the "support for freedom of speech, which is a cornerstone of our democracy, and his decision to instruct Virgin Trains to restock the Mail.
"We are sure the many Mail readers who travel on Virgin Trains will be delighted."
The paper described the original decision as "disgraceful" and suggested it had been taken for "political reasons".
Its had said it "may be no coincidence" the other titles remaining in stock were "like Virgin owner Sir Richard Branson... pro-Remain". The Mail had taken the opposite stance during the EU referendum.
The decision by Virgin Trains had also attracted criticism from Foreign Secretary Boris Johnson, who described it as "censorious and wrong".
When asked about the issue, both a Downing Street source and Labour leader Jeremy Corbyn said they backed a free press, while noting the choice of products sold by Virgin Trains was a decision for the company.