After reviewing answers found in the "Similar Questions" area, I didn't see a definitive answer. To me it seems any writer or speaker is "regarding" something so the word "regard" would be singular. The writer could be regarding several things, but this difference would not automatically dictate the word "regard" to be used in the plural, would it?
The correct usage is the singular with (or in or having) regard to.
He made enquiries with regard to Beth.
The reason why some people confuse the singular with the plural is because there's a similar usage of the word regard in the plural form that is used to to introduce a topic.
As regards content, the programme will cover important current issues.