Security at Parliament's gates was breached last year by an intruder who flashed fake identification and wandered around the estate for 12 hours, it has been claimed.
The Sunday Telegraph said officers at Carriage Gates, where Pc Keith Palmer was stationed when he was stabbed by Khalid Masood in Wednesday's terror attack, were fooled by a 29-year-old who did not have security clearance.
He then wandered around the Palace of Westminster before eventually breaking into Moncrieff's bar in the parliamentary press gallery and was discovered drunk the next morning, it was claimed.
It comes after parliamentarians called for security to be tightened at the entrance, which faces Parliament Square, after a video showed the complex's gates were left open and apparently unmanned after Wednesday's terror attack.
Yards away, separate footage showed Prime Minister Theresa May being rushed from the building and into a waiting car.
A parliamentary spokesman said Commons and Lords authorities were holding a series of "exceptional meetings" on security next week following the atrocity.
One of the plans under consideration could include adding another layer of security outside Carriage Gates in a move which could close the road outside the Commons to all but parliamentary traffic, according to the Mail on Sunday.
The parliamentary spokesman said: "Following the creation of the Parliamentary Security Department in January 2016, security measures in and around the Parliamentary Estate have been reviewed, upgraded and enhanced.
"As is good practice following any significant incident, the Houses, in conjunction with the police and other bodies, are carrying out a review of security around this specific incident (Wednesday's terror attack).
"A series of exceptional meetings are scheduled for next week including a joint meeting of the House of Commons and House of Lords Commissions where the details of the review are expected to be discussed.
"Security of members, staff and the visiting public is our highest priority. For Parliament to fulfil its democratic function, it is crucial that it remain open and accessible to the public."