The 55-year-old, who is battling coronavirus, was admitted to St Thomas' Hospital in central London on Sunday as a precautionary measure but was upgraded to intensive care on Monday after his condition worsened.
"The prime minister is mentally able to make decisions," Ellwood told Sky News. "He's accessible as well.
"What we're going through is unorthodox, we've not been here before, but I have been given assurances that the decision-making process can work in this difficult scenario."
A Downing Street spokesman later said that the PM had had "a good night and continues to improve". body check tags ::