Declaration from contractor's side stating that all the workers employed by him is above 18 years - need some format either in English or Hindi

Hi I am working in a textile company and we have contractors for packing of materials. We want to prepare a one page declaration from contractor's side stating that all the workers employed by him is above 18 years and he will not employee any labour below 18 years. Also, if he employee any child labour and on checking from labour department, if found he will be sole responsible. Like this salient points related to this, i need some format either in English or Hindi.

Hi Maahi,
You can ask for such letter from him where he will declare all the points mentioned by you.
Just to add please make sure to add validity as well and make sure that every year or two, contractor submit fresh letter.

Here is one sample:
To Whomsoever it may concern
This is to certify and confirm that (contractor company name) do not deploy / hire labours / employees under 18 yrs. of age.
If found guilty upon verification, (contractor company name) through its director / partner / proprietor ( name/s here) will be sole responsible for it.
This letter is valid till 31-03-2021
Thanking you
Contractor company name
Signature and Seal
You can change it as per your requirement.