Tenants with one spare bedroom have had a payment reduction of 14% and those deemed to have two or more spare a reduction of 25%.
Lawyers for the 11 cases say that, unless the families move from their homes into smaller properties, they face building up rent arrears and being forced out any way.
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America says it has "identified preparations" for an attack similar to that which killed at least 86, including 30 children, in April.
Despite the rain it will still feel muggy with highs of 22C.
The practice of sending mental health patients far away from friends and family for care has become endemic in the NHS, it has been warned.