Treason laws are to be updated in the UK to cover terrorists and “hostile state activity”, the home secretary has announced.

Following calls for the ancient crime to be updated to cover returning jihadis who have proven hard to prosecute under existing terror offences, Sajid Javid said: “Our definition of terrorism is probably broad enough to cover those who betray our country by supporting terror abroad.

“But if updating the old offence of treason would help us counter hostile state activity, then there is merit in considering that too.”

The proposals are part of a new Espionage Bill being drawn up in the wake of the novichok attacks in Salisbury.

Mr Javid said there were “real gaps in current legislation” and that the government was considering a form of “foreign agent” registration like that used in the US.

Police release images of suspects in connection with Salisbury attack Show all 19 1 /19 Police release images of suspects in connection with Salisbury attack Police release images of suspects in connection with Salisbury attack CCTV – Salisbury train station The two suspects charged in relation to the attack on Sergei and Yulia Skripal at Salisbury train station at 16:11hrs on 03 March 2018 Metropolitan Police Police release images of suspects in connection with Salisbury attack Suspects Suspects Ruslan Boshirov and Alexander Petrov, Russian nationals, approximately 40 years old, who travelled on a Russian passport. It is likely that they were travelling under aliases and that these are not their real names Metropolitan Police Police release images of suspects in connection with Salisbury attack Evidence Bottle and applicator recovered by police from Charlie Rowley’s address in Muggleton Road Metropolitan Police Police release images of suspects in connection with Salisbury attack Evidence A counterfeit perfume box that was discovered by nerve agent victim Charlie Rowley, who later gave it, and the bottle inside, to his girlfriend Dawn Sturgess Metropolitan Police/AFP/Getty Police release images of suspects in connection with Salisbury attack Rowley has previously said he felt lucky to be alive after giving a perfume bottle that contained the nerve agent Novichok to his girlfriend Dawn Sturgess, who later died Metropolitan Police/AFP/Getty Police release images of suspects in connection with Salisbury attack Suspeccts The CPS has issued European Arrest Warrants for the extradition of 'Boshirov' and 'Petrov' in connection with the Novichok poisoning attack on Sergei Skripal and his daughter Yulia in March Metropolitan Police/PA Police release images of suspects in connection with Salisbury attack CCTV – ‘Boshirov' at Gatwick airport Movements in detail - At 3pm on Friday, 2 March, the suspects arrived at Gatwick airport, having flown from Moscow on Aeroflot flight SU2588 Metropolitan Police Police release images of suspects in connection with Salisbury attack CCTV – ‘Petrov’ at Gatwick airport From the airport it is believed that they travelled by train into London, arriving at Victoria station at approximately 5.40pm Metropolitan Police Police release images of suspects in connection with Salisbury attack CCTV – Salisbury train station, 11:48hrs on 4 March 2018 They then travelled on London public transport to Waterloo station and were in the area between approximately 6pm and 7pm. They travelled to the City Stay Hotel in Bow Road, East London, where they stayed on Friday, 2 March, and Saturday, 3 March. On Saturday, 3 March, they left the hotel and took the underground to Waterloo station, arriving at approximately 11.45am, where they caught a train to Salisbury, arriving at approximately 2.25pm Metropolitan Police Police release images of suspects in connection with Salisbury attack City Stay Hotel in Bow Road Police officers stand outside the City Stay Hotel in Bow where on Sunday, 4 March, 'Boshirov' and 'Petrov' made the same journey from the hotel as they did the previous day, again using the underground from Bow to Waterloo station at approximately 8.05am, before continuing their journey by train to Salisbury Getty Police release images of suspects in connection with Salisbury attack CCTV – Wilton Road, Salisbury, 11:58hrs on 4 March 2018 CCTV shows them in the vicinity of Mr Skripal’s house and we believe that they contaminated the front door with Novichok Metropolitan Police Police release images of suspects in connection with Salisbury attack CCTV – Fisherton Road CCTV image of both suspects on Fisherton Road, Salisbury at 13:05hrs on 4 March, 2018 Metropolitan Police Police release images of suspects in connection with Salisbury attack CCTV – Salisbury train station, 13:50hrs on 4 March 2018 They left Salisbury and returned to Waterloo Station, arriving at approximately 4.45pm and boarded the London Underground at approximately 6.30pm to London Heathrow Airport Metropolitan Police Police release images of suspects in connection with Salisbury attack CCTV – Heathrow airport security, 19:28hrs on 4 March 2018 From Heathrow Airport, they returned to Moscow on Aeroflot flight SU2585, departing at 10.30pm Metropolitan Police/PA Police release images of suspects in connection with Salisbury attack Scene investigations The police investigation was carried out over 6 months. Ex-Russian spy Sergei Skripal and his daughter Yulia were found on March 4 in a critical condition on a bench outside the Maltings shopping centre in Salisbury AFP Police release images of suspects in connection with Salisbury attack Victims Former Russian spy Sergei Skripal, right, and his daughter Yulia Rex Police release images of suspects in connection with Salisbury attack Victims Detective Sergeant Nick Bailey who rushed to the aid of the Skripals was also taken to hospital in a serious condition after falling ill when attempting to help them PA Police release images of suspects in connection with Salisbury attack Victims Dawn Sturgess, a 44-year-old mother of three, died after falling ill when partner Charlie Rowley gave her a perfume bottle that contained the nerve agent Novichok Facebook/AFP/Getty Police release images of suspects in connection with Salisbury attack Scene investigations The home of Charlie Rowley in Muggleton Road, Amesbury, where he and Dawn Sturgess were exposed to the deadly nerve agent Novichok PA

The American law requires people who represent foreign powers in a “political or quasi-political capacity” to disclose their relationship and information on their activities and finances.

“We have to ensure that we have the necessary powers to meet the current and evolving threats to the UK, both domestically and overseas,” Mr Javid said, saying the issue should be a “post-Brexit priority”.

“The Espionage Bill will bring together new and modernised powers giving our security services the authority they need to tackle this threat.”

Calls for an updated treason law increased after the UK abandoned efforts to prosecute two alleged members of the Isis “Beatles” cell and stripped Shamima Begum and others of their citizenship to prevent their return.

Former home secretary Amber Rudd, ex-MI5 chief Lord Evans and former Lord Chief Justice are among supporters of a new law.

A paper drawn up by the Policy Exchange think-tank last year suggested defining treason as “aiding a hostile state of organisation” with a new act of parliament.

The report set out a series of actions that could be deemed treason, including helping prepare or commit an attack on the UK, aiding the military or intelligence operations of a state or organisation intending to attack the UK or “prejudicing the security and defence of the UK”.

At the time, the government said it had no plans to change the law or go beyond new offences in the Counter Terrorism and Border Security Act.

Sajid Javid considering banning Britons from travellng to parts of Syria and possibly West Africa

That introduced new offences that made it illegal to click on terrorist propaganda, make “reckless” expressions of support for banned groups, or enter designated areas abroad without a “legitimate reason”.

In his speech in central London on Monday, Mr Javid confirmed that the government was considering outlawing travel to parts of Syria – including the rebel enclave of Idlib – and West Africa.

“The police and security services have worked tirelessly to identify those intending to travel overseas and join Isis,” he said.

“They have seized passports at the border and prevented them from leaving the country.

“And along with concerned friends, families and public-sector colleagues, they have directed hundreds of at-risk individuals to support our Prevent programmes to turn them away from terrorism ... despite this impressive work, the tempo of terrorist activity is increasing.”

Mr Javid revealed that a new far-right terror plot had been foiled.

He said that in total 19 plots – 14 Islamist and five extreme right-wing – had been foiled since the Westminster attack in March 2017.

A total of 30 planned attacks were successfully disrupted in the four years before, and security services have warned of an increased tempo of plots amid record terror investigations.

“Globalisation and the indiscriminate nature of terror means that we are all potential victims,” the home secretary warned, pointing out that more Britons were killed in the Sri Lanka bombings than the London Bridge attack.