The inquiry's leader, Baroness Heather Hallett, has demanded the full documents by a specific date, warning that failure to comply could result in a fine.

Johnson has severed ties with his Government-appointed lawyers and is seeking new representation.

The Cabinet Office argues that the materials requested are sensitive and should not be disclosed outside of government without a valid reason.

Downing Street has stated that it has no duty to disclose "unambiguously irrelevant" material.