LONDON - Britain is preparing to bring in a new spying law and is considering updating treason legislation to counter the threat from hostile states in the wake of the nerve agent poisoning in Salisbury last year, Home Secretary Sajid Javid said on Monday.

Javid said the moves were necessary to cover "real gaps" in existing laws, saying it was important that Britain had the powers to address threats for when it leaves the European Union.

"The conclusion of the Cold War was not the end of state-on-state threats that many had actually predicted. Salisbury was a sharp reminder of that," he said in a speech at London police's Scotland Yard headquarters.

"Getting this right and having the right powers and resources in place for countering hostile states must be a post-Brexit priority."

Plans for a new Espionage Bill come after the Novichok poisoning of Russian double agent Sergei Skripal and his daughter in Salisbury in southwest England in March last year for which Britain has blamed Russia.

Moscow has denied any involvement and says the men Britain has accused of being the Russian agents who carried out the attack were innocent tourists. The incident led to Britain, European countries and the United States expelling 100 Russian diplomats.

Javid said the new spying law would give British security services unspecified "new and modernised powers".

"The areas this work will consider includes whether we follow allies in adopting a form of foreign agent registration and how we update our Official Secrets Acts for the 21st century," he said.

He added that officials had also been asked to consider updating treason laws.

"If updating the old offence of treason would help us to counter hostile state activity, then there is merit in considering that too," he said.

In his speech, Javid also said he could use counter-terrorism powers to make it a crime for British nationals to travel to certain areas in Syria and might also similarly designate parts of west Africa as no-go areas in the future.

He also revealed that Britain's security services had thwarted 19 major terrorist attacks in the past two years, 14 of which were of Islamist origin and five motivated by far-right extremism.

(Reporting by Michael Holden; editing by Guy Faulconbridge) ((michael.holden@thomsonreuters.com; +44 207 542 3213; Reuters Messaging: michael.holden.thomsonreuters.com@reuters.net))