Before the Renters' Rights Act, blanket "No DSS" (no benefits tenants) and "No Children" policies were widespread among landlords and letting agents. While courts had already found these practices to be indirectly discriminatory under the Equality Act 2010, enforcement was inconsistent and many landlords continued to use them.
The Renters' Rights Act makes this explicitly illegal. Landlords and letting agents can't refuse to rent to you, or treat you less favourably, because you receive housing benefit, universal credit, or any other welfare benefit. They also can't refuse you because you have children. Any clause in a mortgage or lease that requires the landlord to exclude benefit recipients or families is overridden by the Act and has no effect.
If you've been discriminated against, you can report the landlord or agent to your local council, which can issue a civil penalty. You can also make a claim under the Equality Act 2010 through the county court.