British-born Khalid Masood was shot dead after killing four people including a policemen on Wednesday when he rammed his car into pedestrians and then tried to force his way into parliament in central London.
The Times showed footage which seemed to suggest that the gate was left undefended while the policeman was being helped - an account government and police officials said they could neither confirm nor deny until the investigation into the attack was completed.
Interior minister Amber Rudd told the BBC there would be another review of security at the Palace of Westminster, but that such arrangements were continually assessed.
