I have found the solution, and it came in the form of a registry patch.
The .reg file included the following text:
Windows Registry Editor Version 5.00
Code:
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\PhishingFilter]
"Enabled"=dword:00000000
Then, in my logon vbs script, I used the following;
Code:
set oShell = CreateObject("WScript.Shell")
oShell.run "regedit /s \\PATH HERE\phishing_patch.reg"
Hope this helps!