Congressman David Cicilline (Democrat) shared the letter on Twitter.
"Together with party colleagues in the Justice Committee, they urge Vice President Pence to invoke the 25th Amendment to remove Donald Trump from office," reports The Hill.
Just hours after a pro-Trump crowd stormed the Senate, demands were made that the incumbent president's term should end before January 20, when the new president will take the oath.
"Even in his video message on Wednesday afternoon, President Trump revealed that he is not mentally healthy and still can not process and accept the results of the 2020 election," lawmakers wrote to Pence.
They continue:
"For the sake of our democracy, we urge you to invoke the 25th Amendment and begin the process of removing President Trump from power.
"The President has shown time and time again that he is not willing to protect our democracy and carry out his duties."
Republican: "Must be removed"
A growing number of Republican leaders and cabinet officials also tell CNN that they believe Donald Trump should be fired before January 20.
Four of them demanded that the 25th Amendment be invoked.
Two others said the president would be prosecuted.
"He needs to be prosecuted and removed," an unnamed current Republican-elected official told CNN.
"Shock for the system"
A former senior official said the president's actions were serious enough to remove him, even though there is little time left in his term.
"I think this has been a huge shock to the system.
How do you keep him in place for two weeks after this? ”
said the former, unnamed, official to CNN.