We have an App which will only be used by internal users. But in order to submit the app for review it is required to submit a username and password, but the app does not have this feature. It is basically a survey app to collect information and will not be available to the general public. Can a app be submitted without this detail.
There's no need to submit it for review in the first place if its not going into the App Store and not available to the general public
in order to submit the app for review it is required to submit a username and password
No it isn't.
I think you might be getting confused on where the username and password is being required. TestFlight requires an Apple Developer Program membership, thus you have to sign in to TestFlight with an Apple ID that has that subscription. There shouldn't be any requirement for the app that you are testing to collect login information for any reason (unless that is part of your app's capabilities, which it looks like is not the case).