(BrE) Both Cambridge and Oxford Advanced Learner's dictionaries allow for both pronunciations. It's long been a joke in the UK that it's controversial how you pronounce controversy.
I seem to remember reading somewhere, probably in David Crystal's 'Stories of English', that the favoured pronunciation used to be on the first syllable, then switched to the second. And for me stressing the first syllable now seems a little strange. But I don't think this is a particularly general rule.
I've noticed for example, with that words that have come from French (probably more recently), such as ballet, where we Brits usually put the stress on the first syllable, Americans often stress them on the second, probably getting closer to the equal stressing of the original French.