most recent month's posts

Hi,
I have a staff news letter, where a monthly issue is published just before the month it refers to.

I need my index page to display the posts for the most recent month of posts. For example:
The current month is July, but the last month of posts was May, so the index page should display Mays posts.

I was using:
`$current_month = date(‘m’);
$current_year = date(‘Y’);
query_posts(“year=$current_year&monthnum=$current_month&order=DESC”)’

But this would only show posts for the current month.

Any thoughts

Thanks