Almost 1,000 police officers from across England and Scotland are being trained up for deployment to Northern Ireland in case of disorder over a possible no-deal Brexit.
Officers from the rest of the UK are to start training over fears violence could erupt from a possible hard border if the UK crashes out of the EU without a deal.
The training is expected to begin this month, the Guardian reported.
Plans were put in place for extra officers after Police Service of Northern Ireland (PSNI) asked for reinforcements, according to the newspaper.
The PSNI request was made under mutual aid arrangements, which are in place to enable local police forces to help each other in times of heightened demands.
The news comes as Theresa May was delivered a huge blow when a new poll revealed most Tories prefer a no-Brexit deal.
The training will mean officers are pulled from their regular duties, as some of the equipment and tactics used in Northern Ireland vary from the rest of the UK.
It is thought the prospect of a large number of English and Scottish police officers being deployed on the streets of Northern Ireland could anger republicans, though.
Irish Prime Minister, Leo Varadkar said Ireland was “now preparing for a no deal with the same level of seriousness that we would” Theresa May’s deal.
Mrs May is pressing European leaders for more flexibility on the Irish backstop as a way of garnering more backbench support for her exit plans.
The National Police Chiefs' Council said: "Police forces continue to prepare for possible eventualities as exit from the European Union draws nearer. As it stands, we have not received a formal request for Mutual Aid support from Police Service Northern Ireland.
"Forces routinely share officers through Mutual Aid. When called on, it is used to ensure an appropriate police presence exists where there is increased demand for it."
