Brent and Ealing are two of the areas most heavily affected by the benefit cap in Britain.
In Brent, there were 2,252 households in February which had been affected by the cap since it was introduced - more than anywhere else in Britain - and almost six in 10 of those families were single parents with children.
Just under half these households were losing up to £50 per week in the cap - but 25 households were losing over £400 per week.
In Ealing, 1,700 households were affected - the third highest total in Britain.
Nearly two in three of them were single parents with children, while 174 were families with five or more children. Nineteen of these families were losing over £400 per week.
In Westminster, 1,444 families have had their benefits capped.
The coalition introduced the cap to make it difficult to be able to claim more in benefits than the average wage of working families.
The cap applies across a range of benefits and once the total money from these benefits reaches the cap limit, money begins to be docked from housing benefit.
The figures are from Department for Work and Pensions statistics, collated by Trinity Mirror's data team.