See How to fix preferences that won't save.

I have followed the suggestions in How to fix preferences that won't save but none have worked.

None of the 3rd party apps mentioned in the article are installed.

User.js file did not exist.

Prefs.js file was not read only. There are no other files related to preferences ie. no prefs-n.js and no Invalidprefs.js

I deleted the Prefs.js file . A new one is created when I opened firefox.

However, even with a new Prefs.js file I cannot get Firefox to permantely remove the tick for "Remember passwords for sites".

Did you check for the presence of a file user.js in the Firefox Profile Folder?

See also http://kb.mozillazine.org/Preferences_not_saved

Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of the add-ons is causing the problem (switch to the DEFAULT theme: Tools > Add-ons > Themes).

• Don't make any changes on the Safe mode start window.

See:

• Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems

Thanks for your reply. The problem was caused by an add-on extension called "FastAccess Web Login". This is installed on my Dell laptop and allows facial recognition to be used as password entry on websites.

I don't use this feature at all but didn't realise this could be causing the issue.

Appears I cannot uninstall this extension as the "uninstall" button is greyed out but disabling it fixes the issue.