Conservative MP Danny Kruger - a leading critic of the bill - said while he welcomed the idea of more experts being involved in the process, he questioned whether they would be impartial like a judge.
He said concerns about the court's capacity to hear individual cases was "a problem for the bill", which should not be proceeding "without adequate judicial safeguards".
Leadbeater said the panel of experts "would be professional people doing a professional job".
She said some would say the bill now had "too many safeguards".
"I've had emails saying why are you making this so difficult? Because we must remember at the heart of this is a terminally ill person who wants choice," she added.
If approved, the bill, which is currently being considered by MPs, would allow terminally ill adults expected to die within six months to seek help to end their own life.
The new proposal will be voted on by a committee of MPs scrutinising the bill. The members were chosen by Leadbeater and the majority support the legislation.
It comes as the committee begins the process of going through the bill line by line.
