As the finance ministry calculates it takes between nine and 22 months to train a customs officer, the Dutch government has green-lighted immediate recruiting, training, tendering of contracts and organising of housing.
Mr Snel wrote to Dutch MPs: "The divisions within the British Conservative Party and the remaining lack of clarity about the British input continue to impede the smooth running of the negotiations.
"It is therefore clear that the scenario that the UK leaves the EU on 29 March 2019 without a withdrawal agreement and without a transitional period is still conceivable.
"The red lines of the UK for the future relationship with the EU (leaving the internal market and customs union) mean that the trade relationship can not go much further than a trade agreement like the one the EU has concluded with Canada."