A north Wales police chief claims he has been gagged from warning people about a possible threat to security and law and order caused by Brexit.
The region's Police and Crime Commissioner, Arfon Jones, said police had been warned against sharing arrangements for a no-deal Brexit.
He claims security at Holyhead port could be compromised by a hard Brexit.
However, one of the groups Mr Jones accuses of gagging him has said there are security reasons for doing so.
Mr Jones claims the National Police and Crime Council (NPCC) and the Association of Police and Crime Commissioners (APCC) have put a gagging order on the country's 41 police and crime commissioners to stop them from sharing policing plans following Brexit.
The NPCC represents police chief officers, while the APCC represents police and crime commissioners.
"In my view, it amounts to a gagging order but we have been elected and we are under an obligation to tell people what's going on in terms of crime and policing," Mr Jones said.
He claims new policing arrangements will be "slower, more cumbersome and more bureaucratic" following Brexit, adding that the UK could be frozen out of up to 32 of the shared services used to target criminals across Europe, including at Hollyhead port.
"Brexit risks putting the UK and North Wales in jeopardy," he said.
But the APCC said some of the material it distributed to commissioners contained "security classifications" which it must adhere to.
Chairman Mark Burns-Williamson added the APCC had highlighted the potential impacts of Brexit on "policing and security matters".
"PCCs have an important role, not only in reflecting the concerns of our communities but in ensuring that there is strategic and financial oversight of the process," Mr Burns-Williamson said.