No there is no duty of care towards a future employer
BUT
if he is asked for a reference then he would be liable for mis-statements ( hedley burke and heller)
that is if he says an employee on asking is good when he knows he is crap then he could be liable for losses caused by the crap employee in his new employ
american refs are
1) did he work for you
2) what was his sick record like
3) would you employ him again - and that is it
so it is different
does he have to offer info to the new employer - no
does he have to tell the truth in a reference - yes
as a Landlord - I have to pay attention to this for tenants references. I cant give them a good ref to get them to leave. - for the really terrible ones I just limit myself to 1,2,3 ( no I would not give another lease)
Hedley is here
https://en.wikipedia.org/wiki/Hedley_Byrne_%26_Co_Ltd_v_Heller_%26_Partners_Ltd
worth a read ....