How do you say 'worse still', with a more business-like tone?

Question

How do you say 'worse still', with a more business-like tone?

Answer 1

Continuing downward trend

Answer 2

'even more detrimental'

Answer 3

Not knowing the context that the term "worse still," it's difficult to offer a sure-fire reply but here are some terms you might be able to use:

"even less effective"

"weaker yet,"

"from a negative perspective,"

While I understand that you are trying to maintain a professional and business-like tone with your message, the main thing is that your message be clear. Given that, "worse yet" may be totally appropriate.