The Chief Constable Simon Byrne has told Boris Johnson the PSNI will not police any customs checkpoints on the Northern Ireland border after Brexit.
Mr Byrne had a 30 minute video call with the prime minister last Friday.
He also told Mr Johnson he had “no plans to put police officers on any one of 300 crossings” along the border.
Speaking after a meeting of the policing board in Belfast, Mr Byrne said the PSNI does not want “to be dragged into another type of policing”.
The prime minister submitted his Brexit offer to the EU on Wednesday.
It would see Northern Ireland stay in the European single market for goods, but leave the customs union – resulting in new customs checks.
The PM’s Brexit plan also set out details of a replacement for the Irish border “backstop” in the current Brexit agreement.
The backstop is the controversial “insurance policy” that is meant to keep a free-flowing border on the island of Ireland but which critics – including the PM – fear could trap the UK in EU trading rules indefinitely.
Under Mr Johnson’s proposals, customs checks on goods traded between the UK and EU would be “decentralised”, with paperwork submitted electronically and only a “very small number” of physical checks
These checks should take place away from the border itself, at business premises or at “other points in the supply chain”
The chief constable has taken legal advice on what he can be asked to do.
He did state, however, that the PSNI would be obliged to support customs or border force staff if they found themselves under risk of attack.
Mr Byrne added he did not want “to interfere in negotiations” involving Mr Johnson and the European Union (EU).
Last year, the PSNI was given money to hire 180 extra officers to help prepare for Brexit.
It now wants government funding for 300 more officers next year, as part of a push towards eventually achieving a police service comprised of 7,500.
Officer numbers are currently around 6,800.
The policing board is fully supportive of the PSNI’s request for increased manpower.