Grammar check

The latter form.

For native speakers, the verb "regret" is normally used with a gerund.

I always regretted never visiting London.
or
I always regretted never having visited London.

http://www.englishpage.com/gerunds/gerund_or_infinitive_different_list.htm

Or a noun:

I have always regretted my remarks to Mary at her wedding.
We regret the inconvenience caused by our error.

Or a pronoun:

Don't say anything you might regret later.
I spoke and instantly regretted it.