US President Donald Trump has moved to formally ban most transgender persons from serving in the military with limited exceptions, according to a White House memorandum.

The memorandum was issued on Friday night on policies determined by Defence Secretary Jim Mattis, stating that transgender persons were “disqualified from military service except under limited circumstances”, reports The Hill magazine.

The memorandum, filed in the US District Court in Seattle, states that “transgender persons with a history or diagnosis of gender dysphoria – individuals who the policies state may require substantial medical treatment, including medications and surgery – are disqualified from military service except under certain limited circumstances”.

Mattis will have some leeway in implementing the policy, the memo states, as will Homeland Security Secretary Kirstjen Nielsen when it comes to the Coast Guard.

The two top officials “may exercise their authority to implement any appropriate policies concerning military service by transgender individuals”, the memo stated.

However, LGBT advocates quickly denounced the move, The Hill reported.

“There is simply no way to spin it, the Trump-Pence Administration is going all in on its discriminatory, unconstitutional and despicable ban on transgender troops,” Human Rights Campaign president Chad Griffin said in a statement.

“The Trump-Pence administration’s continued insistence on targeting our military families for discrimination is appalling, reckless, and unpatriotic,” added American Military Partner Association president Ashley Broadway-Mack.

The Palm Centre, a group that promotes the study of LGBT people in the military, accused the Pentagon of having “distorted the science on transgender health to prop up irrational and legally untenable discrimination that will erode military readiness”.

Trump first called for a ban on transgender troops in a series of tweets last year, and followed up in August by issuing a memo banning transgender people from enlisting.

The ban has since been battled over in court, with Mattis in February giving Trump a final recommendation. It was expected that he would recommend Trump allow transgender troops to remain in the military.

Several federal courts blocked Trump’s initial ban, with one ruling in November that the military would be forced to resume accepting transgender recruits starting this year.

In February, the Pentagon confirmed that one transgender recruit had joined a branch of the military after the ban was lifted due to the court order. That individual passed all tests including medical, officials said.

It was unclear what Trump’s decision will mean for that unnamed recruit and the estimated thousands of other transgender Americans currently serving active duty in the military.

While the exact number of transgender individuals in active duty service is unknown, a 2016 Rand Corporation study commissioned by the Pentagon estimated the number to be anywhere from 1,320 and 6,630, with 830 to 4,160 others serving in the reserves.