Mr Benn, who spent more than half a century on the green benches and served in former prime ministers Harold Wilson and James Callaghan's governments, died aged 88, two weeks ago.
His coffin rested overnight in the crypt Chapel of St Mary Undercroft after royal permission was given. Baroness Thatcher, who died last year, has been the only previous person to receive this honour.
A private ceremony will be held this afternoon and the chapel will then be open so members from both Houses can file past the coffin. He will be buried at the family's Stansgate estate in Essex.