Polite phrase apologizing for irregular (written) correspondence


What is the set phrase used to apologize for not corresponding regularly?




> ご無沙汰しております。

means something like "I apologize for not contacting you for such a long
time".

It is a set phrase which is polite and suited for written correspondence and
thereby satisfies almost all your requirements, except for the fact that it
doesn't mention that you _regularly_ fail to keep in touch. But then, I don't
see how mentioning this would have any positive effect.

As you haven't given a clear context for your question, I should just like to
mention that the above is better suited if the "late" correspondence was
initiated by your letter or email and you are not simply replying late to a
particular letter or email. (For the latter, something like
「返事が遅くなり、申し訳ございませんでした」 would probably be more suited.)

