A hotly-contested intelligence memo which alleges the FBI abused its powers to spy on a US citizen working for Donald Trump has been declassified and released by Republicans.

After the document was made public, Mr Trump said "a lot of people should be ashamed of themselves", going on to imply the memo revealed political bias at the heart of the FBI and labelling it a "disgrace".

The memo came from the Republican party and Intelligence Select Committee chairman Devin Nunes.

It claims that a dossier compiled by Christopher Steele on behalf of the Democrats, which identified links between Donald Trump's foreign policy advisor Carter Page and Russian officials, was motivated by financial and ideological interests which were not declared.

The memo centres on the FBI's surveillance of Page during the 2016 presidential campaign.

To monitor a US citizen, the FBI had to abide by rules outlined in the Foreign Intelligence Surveillance Act (FISA), and ensure the application for its surveillance warrant was signed off by senior judges.

The warrant was renewed a number of times by different judges, suggesting they were suitably convinced by the evidence gathered by the FBI that Page was acting as an agent of a foreign power and should be continued.

However, the memo alleges that neither the original application nor any of the renewals disclosed Steele's links to the Democrats or the Clinton campaign, which funded Steele's efforts to dig up dirt on Trump.

It also claims that what it labels as the "political origins" of the Steele dossier were known to officials at the Department of Justice and the FBI.

Speaking to reporters, Mr Trump said: "I think it's terrible. You want to know the truth? I think it's a disgrace.

"What's going on in this country, I think it's a disgrace."

Taking to Twitter, he went on to accuse the FBI and Department of Justice of an "unthinkable" breach of process.

Meanwhile, Mr Nunes released a statement saying the memo had found "serious violations of the public trust", and said he hoped its release would "shine a light on this alarming series of events."

Democrats have dismissed the memo as a "profoundly misleading" Republican document which is designed to undermine special counsel Robert Mueller's investigation into how Russia may have interfered with the election.

Both the FBI and the Department of Justice appealed for the memo to be kept as classified, arguing that it contained significant inaccuracies.