Boris Karpichkov, a former KGB agent, says he was poisoned on Auckland's Queen St.

A former senior KGB agent who turned double agent then fled to the UK has told of an attempt to poison him in Queen St, Auckland.

Boris Karpichkov made the claims which Prime Minister Jacinda Ardern was seeking to confirm on Wednesday while appearing on Good Morning Britain in the wake of the poisoning in the UK of double agent Sergei Skripal.

Skripal's Spanish links have also seen interest re-emerge in the little-known case of a Russian agent who lived in Madrid under a fake Kiwi identity, apparently stolen from a dead baby, for nearly two decades.

Misha Japaridze Sergei Skripal in 2006, speaking to his lawyer from behind bars seen on a screen of a monitor outside a courtroom in Moscow

​Skripal - a former Russian military intelligence officer who was a double agent for the British in the 1990s and early this century - and his daughter Yulia, 33, are critically ill after being poisoned in England with a military-grade nerve agent known as Novichok developed in the former Soviet Union.

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Karpichkov, a Latvian, was recruited by the KGB. Then when Latvia became independent after the collapse of the Soviet Union he joined that country's intelligence service but continued to work for KGB successor agency the FSB.

CCTV images show Sergei Skripal in his local shop.

After his cover was blown he managed to slip out of Russia, using a false passport he was given as a KGB officer.

Karpichkov has previously said he lived in New Zealand for more than a year after fleeing the UK in 2006 when his life was threatened by Russian security services. He reportedly used a forged Lithuanian passport.

New Zealand police said on Wednesday they were "aware that Mr Karpichkov was in New Zealand between June 2006 and October 2007.

"We are currently examining our files to assess what information we may hold about Mr Karpichkov. Given the historic nature of this matter it is likely to take some time to complete this assessment."

Karpichkov told Good Morning Britain he received a warning by "burning telephone" on February 12, this year, from a FSB operative telling him "something bad" was going to happen to him, Skripal and some other people.

He also talked about the Queen St incident in which, he said, he was approached about 10am by someone who looked like a "common beggar". He had also noticed other people following him.

"I was just walking, carrying my bag, and just looking left side into shop windows, and just noticed with side vision that some person approached me," Karpichkov said. The person tried to grab his bag.

"Next what I felt was kind of dust thrown into my face. Then beggar just walked away".

Karpichkov walked about 50-100 metres then almost passed out, His head was spinning and he started sweating.

That evening his nose and eyes were running, his eyes were scratchy and his chest was covered with a red rash.

A doctor told him he had the common flu but in the next two months he lost 30 of his 90kg.

Another link to the Skripal poisoning to have re-emerged is the case of Russian agent Sergei Cherepanov who lived in Madrid - where Skripal is thought to have been turned by Western intelligence agencies - for nearly two decades under a fake Kiwi identity.

Skripal reportedly took up a position in the Russian embassy in Spain in 1993 or 1994, and is thought to have been recruited by British intelligence in 1995, and given the code name Forthwith.

In 1996, Skripal, who had diabetes, went back to Moscow where he worked for Russian military intelligence, the GRU.

Because of his poor health he resigned in 1999, but continued to make trips to Spain. He was arrested in Moscow in December 2004 and convicted of espionage.

In 2010 he was freed in a spy swap and moved to the UK.

Also living in Madrid at the time Skripal was there was a 50-something man with a bushy moustache, who went by the name of Henry Frith.

According to Poilitico, which wrote about him in mid-2016, he had been in Madrid for almost two decades.

He spoke Spanish with a slight accent, which he attributed to having been born in Ecuador to an Ecuadorean mother and a father from New Zealand.

Frith ran Frimor Consultores, described as a "high value, reliable consultancy and business services company".

He travelled frequently for business, and early one morning in mid-2010 he again flew out of Madrid airport. This time he didn't return.

According to the Independent, he surfaced in Moscow where, under his real name of Sergei Cherepanov, he was welcomed back by his colleagues in the SVR, the Russian foreign security service and reunited with his wife Olga, and son, Andrei.

Politico reported "Western intelligence sources" had told it that Frith/Cherepanov had lived for years under a carefully constructed "legend" - a false identity, complete with a fake history and background.

A European source aware of the Spanish case said Frith had been under watch for "well over a year" before he left Madrid for good.

That gave time for counterespionage services to deconstruct Frith's identity.

The only trace of a "Lawrence Henry Frith" in New Zealand's records was of a boy who died in 1937 in Hamilton, aged one.

The Frith name may simply have been chosen in a cemetery by a Russian embassy employee in New Zealand, Politico reported the source saying.

The commercial registry in Madrid has a record of Frimor. Its founding act was registered in November 1995. It mentioned Henry Frith "born November 9, 1957 … of New Zealand nationality".

Politico said European security services publicised the Frith/Cherapanov case to draw attention to what an official called a "dramatic increase" in Russian espionage activities in Europe.

It includes a le Carre-style scene that played out on Frith/Cherepanov's last day in Madrid.

His double life was brought to an end apparently by the same event that led to the arrest of 10 Russian agents in the US, including the glamorous Anna Chapman.

Those arrests are thought to have come after former SVR official Colonel Alexandr Poteyev fled to the US, fearing he had been uncovered as an American mole.

Some of the 10 US agents had been under surveillance for many years.

On the evening of June 28, 2010 - the day after the 10 US agents were arrested - a man approached Frith/Cherepanov near his home in Madrid.

A European intelligence service provided a transcript of the conversation, although Politico said it could not be independently verified.

The man, apparently a British intelligence agent, asked if Frith/Cherepanov had a few minutes to chat. "I think it's very important that you do," the agent continued. "I have here in my hand your life.… And we must talk … because you are in a very difficult situation," the British agent said.

The agent tried to turn Frith/Cherepanov, but the Russian kept insisting he was Henry Frith. The next morning he was gone.

The Independent article reported a number of sources were saying British and Spanish security agencies had been in liaison since the poisoning of Skripal.

The article said Frith/Cherapanov had already been in Madrid three years when Skripal arrived. The two men had met in Spain.

While running his business, Frith/Cherepanov was also carrying on spying for Moscow, guided by Skripal's diplomatic colleagues Anton Olegovich Simbirsky and Aleksandr Nikolayevich Samoshkin.

Simbirsky and Samoshkin were accused of running Frith/Cherapanov and expelled from Spain.

It's not clear what, if any, damage Frith/Cherapanov did to Spain or the rest of the West.

Politico said a member of an intelligence service told it Frith/Cherapanov had a system that allowed him to directly communicate with Moscow. He would also copy reports onto a USB key that he left to be picked up in so-called "dead letter boxes".

In an amusing incident that sounds like something out of the Rowan Atkinson spy parody Johnny English, pictures from a Western intelligence service purportedly show a diplomat pretending to urinate on the side of a secluded road, look around and take something from under a rock.

An agent told Politico that illegals such as Frith/Cherapanov were mostly used as messengers because "official" spies who worked out of embassies were under surveillance.

The prime minister said she shared the UK's concerns over the use of the globally banned nerve agent, and New Zealand had used an international platform to speak out against it.

Ardern said she hadn't been aware of the incident Karpichkov claimed to have happened in 2006. However, she had sought advice on it from the Department of Prime Minister and Cabinet.

When asked if she was concerned that New Zealand may not be exempt from such attacks, Ardern said that was why she was seeking advice.