MP Alistair Carmichael has asked for a government inquiry into the running of the Driver and Vehicle Standards Agency (DVSA).
Mr Carmichael said the recent actions of the government agency had “greatly eroded confidence” in its competency.
The DVSA has been at the forefront of a number of embarrassing episodes recently.
None of its three theory test centres in Shetland are ready for tests yet – over eight weeks after it announced they would be opening them.
The agency had to cancel all booked tests in Shetland and Orkney for October.
And it has also been left without a testing site for HGV and motorbike tests, although controversial plans have been lodged for the former Scatsta Airport.
Mr Carmichael has now written to transport committee chairman Huw Merriman MP, calling for a parliamentary inquiry into the DVSA.
He said the agency had “haphazardly” cancelled services and had continually contradicted itself.
And he added they were “evasive” and “deaf to outside views”.