Bailiffs were sent to over 12,000 of the poorest Londoners who were behind on their council tax payments last year, a report has revealed.
Two years on since the localisation of council tax support schemes, almost 123,000 low-income Londoners previously deemed too poor to pay the levy are in arrears on their council tax.
Campaigners said cash-strapped local authorities were covering funding gaps by charging reduced council tax charges to low-earners, the unemployed and disabled who had previously been exempt.
A report from the Child Poverty Action Group and Zacchaeus 2000 Trust has found 24 out of 33 London boroughs levied a minimum council tax charge over 2014/15, with four raising the sum low-income households were expected to pay.
While research found 12,000 council tax support claimants in the capital were referred to bailiffs in 2014/15, campaigners said the figure was likely to be 'significantly higher' as data could only be gathered from 13 boroughs.
Researchers warned the situation could worsen as six London boroughs either introducing a minimum payment for the first time or increasing rates for 2015/16.
Child Poverty Action Group chief executive Alison Garnham said: 'This research shows the hit that Londoners previously deemed too poor to pay are taking as a result of council tax localisation.
'Families are saying their budgets just won't stretch to cover the tax. Worse, many are facing court costs piled on top of a debt they couldn't meet in the first place.
'Central government and local authorities must face the fact that the new scheme isn't working. They need to play fair and stop charging council tax to people who haven't got the money to pay it.'
Joanna Kennedy, chief executive of Z2K added: 'At the same time as the government is making great efforts to lift low income households out of income tax it is perverse that local authorities should start to charge them council tax.'