It took almost three hours for a fault with 999 to be reported to the government by BT, according to a minister.
Issues with the emergency line were reported on Sunday and lasted for several hours, with some callers unable to get through to handlers.
The government was asked about what happened in the House of Lords on Monday.
Technology minister Viscount Camrose told colleagues the error was first noticed by BT at 6.30am on Sunday morning, but the government was not informed until 9.20am.
The issue has now been fully resolved, and both Westminster and regulator Ofcom have launched inquiries.
BT has apologised “sincerely” for the issue, which was finally resolved on Sunday evening.
The disruption went on despite the telecoms giant turning to a back-up system.
Lord Hogan-Howe, who headed the Metropolitan Police between 2011 and 2017, called for the removal of BT from the 999 process.
He said the only reason the company was needed was to direct callers to the service they required.
“Why don’t [fire, ambulance and police] answer them together?” he asked.
“Why don’t we remove the cost that BT imposes on the whole system that appears has not worked very well on this particular occasion?”
Viscount Camrose said inquiries would ‘allow us to learn lessons’. Pic: House of Lords
The former Labour MP Ruth Smeeth, who is now Baroness Anderson of Stoke-on-Trent, said: “This is an incredibly disconcerting event. We all rely on the 999 emergency number as our ultimate safety net at the height of distress and vulnerability.
“Any failure in the system will undermine faith in our emergency provision. We are seemingly very fortunate that there was no major incident.”
Highlighting the separate inquiries into the incident, Lord Camrose said: “The combination of all of those will allow us to learn lessons to improve future resilience of the system.”
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He added: “I understand that [BT] informed the government as quickly as it was practically possible for them to do so.
“One of the areas they will look into as part of the inquiry is whether that should have been, could have been, faster.”
