Tavish Scott MSP believes that BT's guarantees to help prevent a repeat of the communications breakdown on the 25th July are inadequate.
While BT promised it would carry out work on the Wideford Hill transmitter in Orkney, they could not guarantee that there would be no future problems.
A spokesperson from BT commented:
"While incidents of this nature are rare, we cannot guarantee a fault-free infrastructure and this is the case UK-wide.
"That said, we're doing everything we can to learn from this and make sure there is no repetition. We apologise once again for the disruption caused."
To which Tavish Scott responded:
"Would Glasgow or the capital of Scotland accept the fact that 999 emergency calls may be impossible through a phone fault? I doubt it.
"There does not appear enough back up or a Plan B. I do not see why people in Shetland should be left wondering whether the 999 number will work or not.
"It must and I am asking all the emergency services to come together and insist on that. That is what we pay our taxes for; safety and security in the very rare moment of absolute need."