The UK will become a less safe place in the event of a no-deal Brexit, law enforcement chiefs have warned MPs, saying that a loss of shared EU information could even lead to some overseas criminals deliberately moving to the UK to avoid arrest.

The head of the National Crime Agency (NCA), Lynne Owens, told the Commons home affairs committee she would be “deeply concerned” about the security implications if the UK left without a deal.

Giving evidence alongside her, Richard Martin, a senior Met police officer who leads on Brexit for the National Police Chiefs Council, said a no-deal could mean officers having to get a court warrant before arresting foreign nationals, even those wanted for serious offences.

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EU countries would face similar barriers in seeking to detain people wanted by the UK, for example if the two Russian intelligence officers sought for the Salisbury nerve agent poisoning had travelled abroad.

The MPs heard that if the UK left without a deal, its police forces would no longer have access to the EU-wide information system linked to the European Arrest Warrant (EAW), the second version of the Schengen Information System, or SIS II. Instead, they would be reliant on an Interpol alert system called I-24/7, which is less complete and not automatically checked by all police forces.

Owens said that reduced access to intelligence could be exploited by criminals: “What we do know is that serious and organised criminals are wily, and therefore they will adapt their behaviour, their working practices, depending on the arrangements that are put in place.”

Asked if that could mean some foreign criminals deliberately relocating to the UK to get out of the reach of the EAW, Owens replied: “That is certainly one of the intelligence judgments that we have to make.”

Martin told the committee that another disadvantage of the Interpol system was that its method of issuing so-called “red notice” alerts did not allow automatic arrest, meaning police in the UK would have to apply to a magistrate before detaining a foreign suspect. This could take hours or even days, Martin said, and it was “unlikely that you’d find them again unless you were very lucky”. This would have “a massive impact”, he said.

Similarly, he told the MPs, while currently it takes a maximum of 10 days to obtain information about an overseas criminal history, in the event of a no-deal this could increase to a maximum of 66 days.

It was not even certain that European nations would “fully embrace our desire to use Interpol”, Owens said.

She said: “So even if we do decide to put a smaller number of wanted people on to the system – some of our highest-risk people – at the moment that information is flagged automatically to our European policing partners, and they take action on it. The new system would require them to actively check the Interpol notices.”

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Asked by the committee chair, Labour’s Yvette Cooper, for their overall messages on the risks of no deal, Owens said there was “a risk that this country is less safe as a result”.

Martin replied: “These entrepreneurs of crime, for want of a better word, will find any gap in the market that they can and they’ll exploit it. And they’ll certainly exploit it across borders. We should not play with security. We need to keep our security safe across the whole of Europe, and if we were to not get a deal, then we are not going to be as safe as we currently are.”