Hi, this is Jim, thank you for the question - I will resolve this for you.
Sorry to hear of the issue. Whilst it is quite comment, you need to get this fraud marker removed and indeed you have a valid reason to do so.
First of all, unless you have already done this, you will need to make a formal complaint to Natwest here:
If they uphold your complaint they can remove the marker. You need to detail why the Cifas marker was unwarranted. If they reject your complaint then ask them for a final response letter (a "deadlock" letter) and then you need to escalate the dispute to CIFAS themselves who will do an independent review of the case. The address to write to is :
6th Floor, Lynton House
7-12 Tavistock Square
That should take no longer than 14 days to complete. If CIFAs agree with the company which registered the marker, you would have to escalate it to the Financial Omudsman Service (http://www.financial-ombudsman.org.uk) who can review the evidence and they can order the CIFAS marker to be removed.
If you want to find out if CIFAS holds any fraud data against your name, you can make a subject access request to them here:
Ultimately, if Natwest and CIFAS refuse to remove the marker, the Ombudsman is your last chance so you do need to go through the process and reach the Ombudsman stage - all being well they will uphold your complaint and the marker will be removed as if it was never put on your credit reports.
I hope this helps and answers the question - please feel free to ask me anything else. .
Have a good day,