WASHINGTON • United States President Donald Trump paid US$38 million (S$54 million) in federal taxes in 2005 on income of US$153 million and reported a US$105 million write-down in business losses, according to a copy of his tax return first revealed on MSNBC.

In an appearance on The Rachel Maddow Show on Tuesday night, Pulitzer Prize-winning journalist David Cay Johnston said that he obtained the returns when they "came in the mail over the transom" but does not know who sent them. The tax returns that Ms Maddow displayed on air showed a stamp that read "Client Copy".

Mr Trump paid an effective tax rate of 25 per cent and saved millions of dollars in additional taxes by claiming the losses, according to the document.

The White House responded without waiting for the show to air, issuing a statement that seemed to confirm the forms' authenticity even as it defended Mr Trump and assailed MSNBC for publicising them.

The statement, issued anonymously and attributed to a White House spokesman, accused MSNBC of unlawfully releasing Mr Trump's tax returns. "You know you are desperate for ratings when you are willing to violate the law to push a story about two pages of tax returns from over a decade ago," it said.

The statement said that Mr Trump, as "one of the most successful businessmen in the world", paid "no more tax than legally required", and added: "Despite this substantial income figure and tax paid, it is totally illegal to steal and publish tax returns. The dishonest media can continue to make this part of their agenda, while the President will focus on his, which includes tax reform that will benefit all Americans."

In a tweet yesterday morning, Mr Trump said: "Does anybody really believe that a reporter, who nobody ever heard of, 'went to his mailbox' and found my tax returns? @NBCNews FAKE NEWS!" He did not immediately explain how he believes Mr Johnston obtained the documents.

Mr Johnston said on the MSNBC show: "Let me point out it's entirely possible Donald sent this to me."

He added: "Donald has a long history of leaking material about himself when he thinks it's in his interests."

Mr Trump's eldest son, Mr Donald Trump Jr, was quick to claim victory over those who speculated that his father paid no taxes. "Thank you Rachel Maddow for proving to your #Trump hating followers how successful @realDonaldTrump is & that he paid $40mm in taxes! #Taxes," he tweeted.

The two pages MSNBC posted online do not reveal anything about Mr Trump's actual sources of income but do reflect the types of income he received: almost US$1 million in wages, US$9.5 million in taxable interest, US$42.4 million in business income, US$32.2 million in capital gains and US$67.4 million from "rental real estate, royalties, partnerships, S corporations, trusts, etc".

It was broadly favourable to the White House and appeared to back up Mr Trump's claim that he paid his fair share of taxes and no more. During his campaign, Mr Trump departed from roughly 40 years of tradition by keeping his returns secret, saying his lawyers had advised him not to release returns while under audit.

Mr Trump will donate his annual presidential salary of US$400,000 to charity, spokesman Sean Spicer said on Monday. "The President's intention is to donate his salary at the end of the year," he told reporters at his daily briefing. "He made a pledge to the American people."

He added: "The way that we can avoid scrutiny is to let the press corps determine where it should go."

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