Fifty-three House Democrats have come out against President Donald Trump's ban on transgender troops.

In a series of tweets late last month, Trump declared that the military will no longer “accept or allow” transgender troops to serve “in any capacity.” The president said that the ban was needed to avoid “tremendous medical costs and disruption” posed by transgender people serving in the military.

In a letter dated August 4, Democrats on the House Armed Services and Judiciary Committees say barring transgender people from military service is unconstitutional.

“It is abundantly clear that any effort by President Trump to ban military service by transgender individuals would not only constitute poor policy but would be unconstitutional on its face,” the representatives wrote.

The letter campaign was organized by Representatives John Conyers, Jr. of Michigan and Adam Smith of Washington state.

“We believe any serious or credible review of the law and the facts in the present case make it clear that the President's proposed ban on transgender people serving in the armed forces will weaken, not strengthen our military, and is blatantly unconstitutional,” the letter states.

Forty-five senators led by New York Senator Kirsten Gillibrand signed a similar letter. In both letters, lawmakers called on Secretary of Defense James Mattis “to advise the president against” the policy change.

On Friday, a White House plan to implement the president's ban on transgender troops cleared the White House counsel's office and is now expected to be delivered to Mattis.

(Related: Trump admin “wants to get rid of transgender service members as fast as they can,” source.)