The Developer's Reference *requires* an ITP for new packages (section
5.1):
Assuming no one else is already working on your prospective package,
you must then submit a bug report (Section 7.1, `Bug reporting')
against the pseudo-package `wnpp' describing your plan to create a new
package, including, but not limiting yourself to, a description of the
package, the license of the prospective package and the current URL
where it can be downloaded from.
However, this does not reflect common practice. It's unlikely that we
can change practice (too many DDs think that the Developer's Reference
is not authoritative), so we should change that section to require
that someone who starts working on a new package checks upload/new by
some means.
Filing an ITP should be required only for packages that are
non-trivial to create. If substantial work is required, the package
might not end up in upload/new fast enough to prevent duplicate work,
otherwise upload/new appears to be sufficient to work around the race
condition.
(This is related to bug #259008.)
