Yes, the DVLA has the legal authority to clamp or tow away vehicles as part of its work in combating evasion of road tax (VED).

Do not attempt to remove the clamp, as this could result in further fines and a potential court summons. Instead, call the number that the DVLA has left on the vehicle. You can appeal if you feel you've been clamped and fined unfairly, but you'll need compelling evidence to show why this was unfair when your car was untaxed and not on a SORN.