The telecoms firm last week dodged a bullet when the regulator, which pushed further reforms of Openreach rather than forcing it to be spun off into a separate company.
Soubry rallied against the decision, saying Ofcom was "too soft" and slammed BT for "failing to deliver", adding that it had been given "enough second chances".
"It's not good enough. It's outrageous in this day and age to not have access to super fast broadband and mobile phone signals - and that includes on our trains too," she said, speaking to the BBC's Today show.
"Not only would I have put a very sharp toe under BT and looked at its performance and actually considered splitting it up, making sure it did a proper job - and I'm far from convinced that it's done a proper job."
She criticised BTs figures which claim 90 per cent of the country have access to super fast broadband and said she believes the figures are flawed.
"I don't trust these figures at all. We're told that 90 per cent of properties have access to super fast broadband. It's strange that in my time as business minister, I seemed to meet every member of the 10 per cent," said Soubry.
Soubry called for super fast broadband to be considered a fourth utility under law to get it to more people.
A BT spokesperson said: "“We disagree with Ms Soubry’s comments regarding the separation of Openreach. We fail to see how a smaller, independent Openreach would be able to invest the £1.4bn each year that it does currently.”
“Independent data clearly shows that 91 per cent of UK premises have access to superfast speeds today and this will rise to 95 per cent by the end of 2017. Numerous independent reports, including those from Ofcom and the EU, consistently rank the UK number one amongst our main European peers for superfast broadband coverage and take-up."
The company also pointed out that 99 per cent of the premises in Soubry's constituency of Broxtowe in Nottinghamshire had access to superfast broadband speeds of 24 megabits per second (Mbps) and more than 90 per cent access to ultrafast speeds of more than 100Mbps via alternative networks.