Overpayment of Child Benefit being deducted from ESA? 

My client has an overpayment of Child Benefit which is currently being deducted from his IR ESA.  I have spent some time trying to find authority for these deductions in the legislation but have drawn a bit of a blank.  The nearest I have to is The Social Security (Overpayments and Recovery) Regulations 2013, 
reg 10 Recovery by deduction from benefits http://www.legislation.gov.uk/uksi/2013/384/regulation/10/made

but not sure this applies to Child Benefit - I appreciate this is a social security benefit but it is not administered by the DWP??

My colleagues suggest the maximum amount which can be deducted is £11.90 if it is not a fraud issue but again the legislation I have found suggests it can be “an amount equivalent to 40 per cent. of the age-related amount applicable to the liable person as specified in regulation 62(1)(b) of the Employment and Support Allowance Regulations 2013(1).”  The Social Security (Overpayments and Recovery) Regulations 2013, reg 13
http://www.legislation.gov.uk/uksi/2013/384/regulation/13/made

hoping you may be able to throw me a lifeline as I feel I am drowning in legislative niceties…

Child benefit overpayments are recovered under The Social Security (Payments on account, Overpayments and Recovery) Regulations 1988.

The maximum amount that can be deducted is currently £11.10 if it isn’t a fraud issue. (Reg 16(4)(b))