For a long time BlackBerry was the de facto choice for businesses looking for a secure mobile device.

But BlackBerry appears to be losing its security advantage over the iPhone in the eyes of IT leaders, and in doing so giving up its last remaining advantage over Apple handsets in enterprise.

Since the iPhone launched in 2007 Apple has been slowly increasing security of iOS devices: adding 256-bit, hardware-based encryption for data stored on the device, widespread VPN support and limiting access that each app has to files and hardware resources on the phone. That’s in addition to its screening of all software on the app store and centralised control provided by third party mobile device management software.

And while the BlackBerry 7.1 devices provide administrators with granular control over users via BlackBerry Enterprise Server and corporate grade security when it comes to the likes of encryption and password protection – it seems CIOs and industry experts believe Apple can now provide the security most corporates need.

John Turner, IT director at accountancy network BDO LLP, said that after years of being a BlackBerry shop he could no longer see any reason not to let his 2,500 staff use Apple iPhones at work.

“The differentiation in the corporate world used to be security, but that has been significantly eroded to the point where it’s gone away now,” said Turner at a roundtable event organised by disaster recovery specialist Sungard Availability Services.

“I’ve satisfied myself that Apple is there or thereabouts [when it comes to corporate security], I think that Apple have caught RIM up.”

Not only has the security of iOS devices themselves increased, Turner said, but mobile device management (MDM) platforms are now sophisticated enough to handle unwanted behaviour, such as jail breaking iPhones, and to allow administrators to manage multiple varieties of handset.

Staff at BDO can already access a variety of corporate systems through work issue BlackBerrys. Once BDO has a new MDM platform in place – it finishes evaluating platforms this week – it will allow staff to access its systems through their own iPhones, as well as start issuing iPhones and iPads as corporate devices alongside BlackBerrys.

In Trend Micro’s recent ranking of which smartphone handsets had security features best suited to enterprise the Apple iPhone came out second, just behind BlackBerry.

Rik Ferguson, director of security research and communication for EMEA for Trend Micro, said: “Apple recognised long ago that having successfully reinvigorated the consumer smartphone market, they needed to make some big technological changes to really compete and gain acceptance in the enterprise space, and they have been steadily adding features over time.”

As in many workplaces, demand from BDO staff to use their personal iPhones at work – the so-called BYOD trend – was a factor in driving Turner to reconsider corporate support for iOS devices.

“People are using iPhones and iPads in their personal lives and asking the question why can’t we use them within the company,” he said.

Ferguson predicted that BYOD will continue to drive uptake of iPhones into the workplace: “It should come as no surprise that Apple are finally taking on BBOS and RIM on their home turf, the release of iPhone 5 is expected to see a huge surge in handset sales and that can only lead to more consumerisation of enterprise handsets.”

If RIM is to fight back against Apple’s encroachment into the enterprise via BYOD, Ferguson said, then it needs to really needs provide a user experience that also appeals to the consumer with its forthcoming BlackBerry 10 OS.

“They already have the minds of the enterprise but they need to be aiming for the hearts of consumers, and that’s a tall order.”

A spokeswoman for RIM said the company was “unable to provide a comment”.