A probe into alleged FBI bias against Donald Trump has been quietly and unceremoniously ended by House Republicans.

The president’s allies in congress say more investigation is needed over the handling of inquiries into Hillary Clinton’s emails and Mr Trump’s ties to Russia by the FBI and the Justice Department.

Despite the year-long investigation, the chairmen of two House committees failed to produce a full report, and instead made public a letter on Friday evening alleging “seemingly disparate treatment” the two probes received in 2016.

House judiciary chairman Robert Goodlatte and oversight chairman Trey Gowdy, who are both retiring next week when Democrats gain a majority in the House, called on the Justice Department to appoint a special counsel to investigate further.

In the letter to the Justice Department and senate majority leader Mitch McConnell, they said they reviewed thousands of documents and conducted interviews that “revealed troubling facts which exacerbated our initial questions and concerns”.

Republicans have said since the election they believe Justice officials were biased against Mr Trump when they started an investigation into his ties to Russia and cleared Ms Clinton in a separate probe into her email use.

The wrapping up of the congressional investigation was a quiet end to a probe that was conducted mostly behind closed doors, but also in public as Republican lawmakers often criticised interview subjects afterwards and suggested they were conspiring against Mr Trump.

The investigation’s most public day was a 10-hour open hearing in July in which former FBI special agent Peter Strzok defended anti-Trump texts he sent to a colleague as he helped lead both investigations.

Mr Strzok fought with Republican lawmakers in a riveting spectacle that featured him reading aloud from his sometimes-lewd texts, and Democrats and Republicans openly yelling at each other.

Mr Goodlatte and Mr Gowdy laid out several concerns in the letter, many of them echoing a report issued this year by the Justice Department’s internal watchdog.

Republican congressman Ryan Costello calls Trump's an 'angry 8th grader' for 'close the border' tweet

That report concluded Mr Strzok’s anti-Trump text messages cast a cloud on the agency’s handling of the probe and also that fired FBI director James Comey repeatedly broke from protocol, including when he announced his recommendation against charging Ms Clinton.

But unlike the congressional investigation, the report also found there was no evidence Mr Comey’s or the department’s final conclusions were motivated by political bias towards either candidate.

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Democrats have blasted the GOP-led congressional probe, saying it was merely meant as a distraction from special counsel Robert Mueller’s Russia investigation.

New York representative Jerry Nadler, the top Democrat on the judiciary committee, and Maryland representative Elijah Cummings, top Democrat on the oversight panel, are expected to end the investigation when they take power in January. Mr Nadler has called it “nonsense”.

California representative Adam Schiff, who does not sit on either panel but is the top Democrat on the House intelligence committee, tweeted on Friday evening that the Republican investigation is ending “not with a bang, but with a Friday, buried-in-the-holidays whimper, and one foot out the door”.

The Republicans have insisted that they were not trying to undermine the Mueller probe.

“Contrary to Democrat and media claims, there has been no effort to discredit the work of the special counsel,” Mr Goodlatte and Mr Gowdy wrote in the letter. “Quite the opposite, whatever product is produced by the special counsel must be trusted by Americans and that requires asking tough but fair questions about investigative techniques both employed and not employed.”

Republicans have repeatedly asked for a special counsel to look into the 2016 questions, but former attorney general Jeff Sessions never granted their request. The department is now led by acting attorney general Matt Whitaker, a Trump ally who has not weighed in on the issue.

The Republicans sent the letter not only to Mr McConnell but to several other Republican senate committee chairmen, including South Carolina senator Lindsey Graham, who will become chairman of the senate judiciary committee.

Mr Goodlatte and Mr Gowdy wrote that “while congress does not have the power to appoint a special counsel, congress does have the power to continue to investigate. They said they believe “the facts uncovered thus far” warrant continued oversight.

The two chairmen have also asked for the Justice Department release transcripts from their investigation. The committees sent the transcripts to the department last week so they could be reviewed for any classified information, but they have not been released.