In their complaint filed in Washington DC federal court, the members say that Mr Trump's directive, expressed on Twitter, has already unsettled and destabilised their "reasonable expectation of continued service". They added that the White House has turned the President's tweets into "official guidance, approved by the White House counsel's office, to be communicated to the Department of Defense."

The five anonymous plaintiffs, named in the case as Jane Does, are identified as service members who "collectively have served this nation for decades in various branches of the US military" and have "informed their chain of command that they are transgender" since last year's policy change.

Mr Trump announced in a series of tweets last month that he would reverse a decision by his predecessor President Barack Obama to allow transgender people to serve openly in the US armed forces. The directive sparked uncertainty about the future of thousands of transgender people already serving in the US military.

"The United States Government will not accept or allow...transgender individuals to serve in any capacity in the US military," Mr Trump wrote. "Our military must be focused on decision and overwhelming...victory and cannot be burdened with the tremendous medical costs and disruption that transgender in the military would entail."

In their complaint, the service members wrote that to reinstate a ban on open service by transgender people "violates both the Equal Protection component of the Fifth Amendment and the Due Process Clause of the Fifth Amendment to the United States Constitution".

Attorneys for the service members asked a federal judge to block the implementation of Mr Trump's directive immediately.

Neither the White House nor the Department of Defense have yet conveyed or promulgated a new policy on transgender service members.

General Joseph Dunford, chairman of the Joint Chiefs of Staff in the US military, previously said there will be "no modification" to the military's transgender policy after Mr Trump's tweets until the directive had been received by the Secretary of State and guidance for implementation had been issued.

Mr Trump's directive came just weeks after Defence Secretary Jim Mattis said the government was reviewing the issue to determine if allowing transgender individuals to enlist would impact its "readiness and lethality".

But Mr Trump's comments were widely condemned within the military including by 56 former generals and admirals, while transgender soldiers dared the US President to kick them out and criticised him for being a "war dodger".

The White House did not immediately respond to The Independent's request for comment regarding the lawsuit.

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