Home Office officials are “not being straight” with MPs over the security implications of no-deal Brexit, Yvette Cooper has said.

In heated scenes at the Home Affairs Committee, the Labour chair repeatedly asked what information the Border Force will lose if the UK is excluded from the Schengen Information System (SIS II) database in March.

The database, which contains details of terrorists, criminals, missing people and objects, is currently checked by British police officers, border and immigration officials 1.4 million times every day.

Paul Lincoln, director general of the Border Force said that without SIS II, officers would be checking “different information” on people arriving at the UK’s border.

He repeated the home secretary’s wording that the situation would be “sub-optimal” but would not give details of what could be lost when pressed.

“I don’t understand your reluctance on this, are we going to lose significant intelligence information and if so, on what scale?” Ms Cooper said.

“Surely parliament has the right to know…whether or not there is going to be less security information available to our Border Force officers when making a decision about whether or not to let somebody in the country.”

Mr Lincoln said he could come back to the Home Affairs Committee with more information, adding: “We are doing all that we can to mitigate the disruption.”

Shona Dunn, second permanent secretary at the Home Office, said discussions on intelligence sharing were ongoing with Interpol and other bodies.

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After marching through central London, there will be a rally on stage in Parliament Square, including speeches from Mayor of London Sadiq Khan. 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When asked precisely what systems the UK would use instead of SIS II she replied: “It’s extremely difficult for us to say at this point.”

Ms Cooper pointed out that there was only five months until Britain leaves the EU and added: “It is really hard to have any confidence in your processes of contingency planning for no-deal if you don’t know, as a basic question, what the scale of security downgrade is.

“If you are going to have to find this information through other routes or do additional checks, you’re going to have to need extra staff.

“How are you going to reassure the British public that borders are not going to become less secure as a result of no-deal?”

Ms Dunn repeated that there would be a “range of mitigations” and that it “depends on the circumstances” whether officials will be left with more or less security information on people arriving in the UK.

Ms Cooper told the panel: “You’re not being straight with us, and I really think at this stage in the process when parliament is going to have to make some decisions about whether there is no-deal or not, I think you really have an obligation to be straight with us about what the security issues are.”

Lynne Owens, director general of the National Crime Agency, said the loss of SIS II, Europol membership and other EU systems would have major implications for British law enforcement.

She said that instead of automatically accessing SIS II as they do now, officers will have to call colleagues in member states for information.

“The best we can come up with is a very manual system,” she added. “Serious and organised criminals will adapt their behaviour and working practices on the basis of what is put in place … if we don't have access to these tools there is a risk that this country is less safe as a result.”

Ms Owens also warned that countries including Germany may have to pass new laws to share information passed through Europol with the UK.

Chancellor Philip Hammond says a no-deal Brexit would result in a new budget

She said that although the UK may apply for associate membership of the policing body, it would lose a “leadership voice on priorities”.

Several nations also have constitutions of practices that would forbid extraditing their citizens to the UK for prosecution outside the European Arrest Warrant system.

The committee was told that around 500 police officers will work to minimise the impact of a no-deal Brexit, including delays to extraditions, criminal records checks, missing person’s enquiries and obtaining evidence from abroad.

Deputy assistant commissioner Richard Martin, of the National Police Chiefs’ Council, said officers have been mapping “fall-backs” for each European tool.

“None of the contingencies are as effective or efficient as the tools we currently use,” he added, explaining that if Interpol’s i24/7 database was used as an alternative to SIS II, officers would not be able to arrest suspects on it without a magistrates’ warrant.

Ms Owens said it would require EU countries to “actively check” the UK’s records on wanted people, rather than cases being flagged on their own systems.

The Home Affairs Committee previously condemned the British government and the EU for putting public safety at risk by refusing to cross political “red lines” in negotiations.

Theresa May’s refusal to submit to European Court of Justice jurisdiction has been a major stumbling block for database access.

The government has said it is confident that an “ambitious agreement on future security cooperation can be reached” after drawing up a proposed security treaty with the EU.