On Friday, the City of London Corporation said there were "no current plans" to ramp up security measures on the bridge.
The decision has now come under scrutiny following the jihadist rampage, which left seven people dead and 48 others injured.
The bollards could have protected pedestrians from being mowed down by the attackers' van as it mounted the pavement.
At least one of the dead is thought to have been killed by the impact of the speeding vehicle.
The terrorists jumped out of the rented van after it crashed and began stabbing revellers in nearby restaurants and pubs.
The first victim of the attack was named earlier this morning as Canadian national Christine Archibald, 30.
Officials ruled out installing anti-terror bollards on London Bridge London terror raids Sun, June 4, 2017
Police have raided a block of flats in Barking in connection with last night's London Bridge terror attack.
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As police continue their investigations following the June 3 terror attacks, a block of flats in Barking is raided for possible suspects
London suffered a similar attack in March, when terrorist Khalid Masood smashed his 4X4 car into people along Westminster Bridge.
Following the atrocity, in which four people were killed, anti-terror barriers were installed outside Buckingham Palace and Windsor Castle.
But many areas in London remain vulnerable to copycat attacks.
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Similar bollards outside Parliament after March’s Westminster attack
News agency Triangle News contacted Mayor Sadiq Khan's office and City of London officials last week.
In an email, they warned London Bridge "seems to be a weak spot" following the Westminster massacre because the pavement is so narrow.
A spokeswoman for the City of London Corporation replied: "There are currently no plans for the provision of barriers or bollards to be deployed at London Bridge."
Mr Khan's office did not reply to the email, the news agency said.
Seven people were killed in Saturday's night horrific ISIS attack
Social media users have pointed out the vulnerability of London Bridge since the attack, which has shocked the nation.
Tom Buckley tweeted: "Terrible scenes at London Bridge. However security there has been shocking since Westminster attack. No bollards, nothing."
Matthew Miers added: "Why hasn't anyone thought of putting massive bollards on London Bridge to stop people driving across the bridge aiming for people?"