Does a UK company have an ethical responsibility to ensure an indian
sub-contractor provides staff with the same working conditions and
saleries as staff in the UK.

N.B I need a summary of the different regulations for india and uk if
possible.

I would imagine that most companies structure salaries according to
local conditions and not according to an absolute scale that applies
all over the world.

Legally no. Ethically, perhaps to provide equally for the health and
safety of Indian workers. If salaries needed to be matched, few UK
companies would do business in India, so I think it is unrealistic to
try to place that sort of guilt trip, unless your objective is to rid
India of investors from the UK. I live in the USA, but I have worked
in several foreign countries. Gennerally it is very bad business to
try to micro manage sub-contractors.   Neil