Abigail Ashford, a solicitor advocate with Stokoe Partnership, who represents clients in the Crown court, said the reforms risked trust in justice.
"Judge-only trials risk deepening existing inequalities and eroding confidence among communities who already feel marginalised," she said.
"In complex or sensitive cases, removing the community from assessing credibility and fairness undermines trust in a way that cannot be compensated for by concentrating decisions in the hands of a single judge."
And Riel Karmy-Jones KC, chair of the Criminal Bar Association, said that it was not juries that had caused the unprecedented delays - but years of underfunding.
"Imposing an untried, untested layer of complexity and cost in the form of any new division of the Crown Court on our desperately underfunded system with its crumbling infrastructure is counter intuitive," she said.
Many criminal barristers blame the previous Conservative government for the backlogs - saying that the courts have been starved of resources for more than a decade.
Robert Jenrick MP, shadow justice secretary, said David Lammy had extensively defended juries in the past - and accused him of abandoning his principles.
"Labour have chosen to spend billions of extra pounds on benefits payments rather than funding the courts to get the backlog down," he said.
Additional reporting by Rachel Muller-Heyndyk