You can use backdoor to describe an action or process if you disapprove of it because you think it has been done in a secret, indirect, or dishonest way.
[disapproval]
He did the backdoor deals that allowed the government to get its budget through Parliamenton time.
He brushed aside talk of greedy MPs voting themselves a backdoor pay rise.
2. singular noun
If you say that someone is doing something through or by the backdoor, you disapprove of them because they are doing it in a secret, indirect, or dishonestway.
[disapproval]
Dentists claim the Government is privatising dentistry through the back door.
backdoor in British English
or back-door (ˌbækˈdɔː)
modifier
carried out covertly and without public or official knowledge and approval; done 'by the back door'
He did the backdoor deals that allowed the government to get its budget through Parliamenton time.
He brushed aside talk of greedy MPs voting themselves a backdoor pay rise.