The city's security against terror threats must be at the heart of European Union negotiations, warned Mayor Sadiq Khan.
In the first joint London Assembly meeting with Metropolitan Police Commissoner Sir Bernard Hogan Howe, Mr Khan highlighted how important the key relationships and systems built up with European partners are to the city's safety.
Promising to take up the issue with the Home Secretary, he said: "I am determined to do everything in my power to ensure that Brexit does not damage the critical relationships and systems we have built up with Europe over many years to ensure this city’s security.
“In order to retain the benefits of the European Arrest Warrant and Prüm, it is paramount that London gets a seat at the table — alongside Scotland, Wales and Northern Ireland —throughout negotiations with Brussels.
“As Mayor, it is my job to protect London’s interests at every stage of the process and I will fight to preserve every possible apparatus at our disposal to help keep London safe.”
'Shocking' rise in hate crimes will be 'stamped out'
The Mayor and the Commissioner also addressed the increase in hate crimes recorded since the vote to leave the EU.
Addressing the Assembly, they highlighted their commitment to stamping it out with a zero-tolerance approach and called for all Londoners to report any incidences of abuse.
West Londoners have reported hate crimes including "racially motivated" graffiti on Hammersmith's Police Centre as well as anti-semitic markings at a church in Ealing .
Mr Khan said: "We have seen a shocking rise in hate crimes in the last two weeks and both I and the Commissioner are determined that we stamp this out right away.
"I have asked the police to be extra vigilant.
"And the Commissioner and I have agreed that we must have a zero-tolerance approach and that the full force of the law must be used to catch and punish any perpetrators."
He added: "I would appeal to all Londoners to report any incidents of hate crime or abuse – we can’t fix this problem unless it is reported.
"We are sending out a very clear message that this kind of behaviour is not acceptable and people will not get away with it."
How do EU agreements help keep London safe?
Agreements such as the European Arrest Warrant and Prüm play a crucial role in allowing the police to do their jobs, helping to keep Londoners safe and bring offenders to justice.
The European Arrest Warrant was successfully used in 2005 to extradite the failed London bomber Hussein Osman to face justice in the UK in a matter of weeks.