Lord Ricketts, who advised the Government on security between 2010-12, said the Government needs to step up its planning to replace EU policing and security measures in the event of no-deal.
He warned the lack of action is “putting the safety of the public at risk”.
It comes after little progress was made during the latest round of talks between the UK Chief Negotiator David Frost and his EU counterpart Michel Barnier, which took place from Monday to Thursday in London.
Neither side is backing down on fishing rights, so-called level playing field guarantees, governance of the deal and the role of the European Court of Justice.
The chairman of the Lords EU Security and Justice Sub-Committee has written to Home Office minister James Brokenshire urging him to make arrangements for future policing and criminal justice cooperation after December 31.
The independent crossbench peer said: “Compelling evidence has been laid before the committee and its predecessors about the significant consequences for law enforcement in the UK if there is no deal on policing and criminal justice cooperation.
“This stands in stark contrast to the Government’s optimism that they have plans for non-EU alternatives that can substitute effectively for the exceptional levels of cooperation the British law enforcement and justice communities currently enjoy with their colleagues in EU countries.
“Without a deal, the loss of operational effectiveness for UK law enforcement agencies – including in Northern Ireland – will be profound, undermining modern intelligence-led policing and putting the safety of the public at risk.
“We urge the Government to address these issues as a matter of urgency.”