Customs and Border Protection workers have been told that under the new ''mandatory reporting'' regime, they will be expected to report on their colleagues' behaviour inside and outside of work.

Under a section titled ''If it doesn't seem quite right'', one directive reads: ''While you are off-duty and at a party you observe a fellow Customs and Border Protection officer smoking marijuana. Report it.''

Another tells staff: ''While walking past a colleague's computer you notice the colleague looking up the details of an ex-partner on the system. Report it.''

Customs staff were assured that such reporting ''is not about dobbing people in'' but they could expect to be disciplined if they ''make a negative comment on Facebook about a specific Customs and Border Protection corporate decision made by the senior executive''.

Paranoia within Customs has been fuelled by recent revelations that a few officers have been socialising out of hours at nightclubs and gyms with Middle Eastern crime figures and members of bikie gangs, including the Comancheros. Some Customs staff are understood to be romantically linked to known criminals. One crime figure was invited to a Customs' Christmas party.

From Friday, staff were told it would be ''a legal mandatory requirement for all Customs and Border Protection workers to report any suspected serious misconduct''. Staff who witness ''serious misconduct'' and do not report it will be investigated and could lose their jobs.

Under the new drug and alcohol testing regime, which begins next month, Customs staff can expect to be tested for drugs and alcohol any time during work hours. The legal blood alcohol limit to drive is 0.05 per cent but Customs is introducing a limit of 0.02 per cent.

One section of the document states that staff can only drink alcohol at ''designated social venues'' in their off-duty hours, but a Customs and Border Protection spokesman clarified that this applied only to venues on Customs premises and that ''there is no restriction on which venues officers can attend outside work hours''.

Asked why it was necessary for staff to report colleagues for smoking marijuana in their own time, the spokesman said: ''Any form of illicit drug use by a Customs and Border Protection officer is incompatible with their role of protecting the border.''

He said negative Facebook commentary could be incompatible with the Australian Public Service Code of Conduct.

The acting deputy secretary of the Community and Public Sector Union, Rebecca Fawcett, said that while the union's members were ''broadly supportive'' of the direction of the reforms, they were worried about other measures.

''The announcement this week by [acting CEO] Mr [Michael] Pezzullo to launch a new 'crackdown' on poor appearance and presentation because it is a 'breeding ground for potential serious misconduct and corruption' is frankly insulting,'' Ms Fawcett said.

Andrew Stewart, a workplace law specialist at the University of Adelaide, said the intrusions were ''significant overreach'' and he was troubled by the limits on speech imposed by the regulation of Facebook messages.