Is this in the uk? Assuming the parent is renting I'm pretty sure the parent can just refuse and the landlord will need an injunction to get in. Good luck getting one in this period.
The right of quiet enjoyment of your home trumps any contractual provision of inspection.
Whilst it's true that even with contractual access rights landlords may not have an actual right to enter (absent an emergency), I'd be careful here... (1) if the landlord or agents turn up anyway and have keys then you'd be relying on calling police to turf them out - who may not side with you whatever the rights and wrongs, (2) it's actually not completely certain legally that quiet enjoyment trumps other rights - as I don't think there have been recent test cases (bear in mind that almost all tenancy agreements do include pretty broad access rights for the landlord to undertake maintenance these days) and (3) if you do refuse access unreasonably and despite a contractual right of the landlord then the landlord may be entitled to damages from you if that delay harms them financially.
The right of quiet enjoyment of your home trumps any contractual provision of inspection.