MPs warned last month that security at Parliament's main gates was so weak it could put police officers at risk.
The Telegraph understands that police have raised repeated concerns about the security of the gate, which has been described as a “weak point”.
In February the House of Commons administration committee discussed the issue, with a particular focus on the “flimsy” and “Meccano” crowd-control barriers in front of the wrought-iron gates.
The barriers have to be manually opened by police on the pavement outside Parliament, which MPs said put them at risk. The MPs called for them to be replaced with a stronger, automated gate which police could operate remotely.
It also emerged on Thursday that Masood was shot dead by a plain-clothed member of the personal security detail of Sir Michael Fallon, the Defence Secretary.
The disclosure led to growing questions about where firearms officers were at the time of the attack, especially as Masood was shot just three unlocked doors away from the Prime Minister.
There were also calls for stronger security measures on Westminster Bridge, where Masood injured 20 people and killed two after driving into them. A previous security bridge has recommended that bollards should be used on roads which are heavily used by pedestrians.
Lord Carlile, a cross-bench peer and former independent reviewer of terrorism legislation, raised concerns about the fact Masood was able to use a cycle-lane as he ploughed into pedestrians.
He said: "We may have to look at the new traffic arrangements around Westminster, which have changed in the last few months and opened up a wide new cycle lane along which this vehicle travelled uninterrupted."
MPs discussed the security concerns about Carriage Gates on February 6. The crowd control barrier was due to be replaced by the end of the year, but plans are now likely to be brought forward.
Sir Paul Beresford, the Tory MP and chairman of the administration committee, said: “There were concerns about security issues in all sorts of ways. As far as I'm concerned the present gates are flimsy and made of Meccano.
“We wanted something that can be operated more easily by the police that will also stop pedestrians.
“At present two police officers have to open them out, they aren't armed. Therefore they are at risk. You can just push past them.”
Tom Brake, a Liberal Democrat MP and member of the committee, suggested that the gate should be closed off to vehicle access entirely.
He said: : “My personal concerns about the Carriage Gates is that this is clearly the weakest link. It is a vulnerable point where MPs, peers and other staff can gain vehicular access to the palace in a way that could allow people to gain access on foot via that route.
“You may have to stop that being a vehicular access so all vehicles come through Black Rod's entrance [at the House of Lords].”
One senior MP said: “One of the slight issues is that we have had car security suitable for terrorist incidents by the IRA. You need a double gate. It is awfully easy to climb over the top."
Alan Johnson, a Labour former home secretary, said the Carriage Gates were a point of vulnerability for the Palace of Westminster, particularly during votes when they were left open to give easy access for ministers.
He said: “When the votes are on, the gates are open so that ministers can drive in from wherever they are in their different departments in Whitehall.”
Nicky Morgan, a Tory MP and former Education Secretary, said she did not think that there needs to be more security in Parliament.
She said: "I think there is a very significant presence of armed officers and police there, and security personnel, and although tragically an officer lost his life, actually the attacker only got 20 metres inside the perimeter. But of course there will be things that need to be looked at but I think we don't want to be working in a fortress.
"MPs know that we are high-profile targets individually but this is about an attack on the Palace of Westminster and MPs obviously will keep their own security under review."