Arron Banks's Russian mother-in-law has denied the tycoon has any financial dealings with Moscow, as the Brexit backer faces a criminal investigation over his donations to the Leave campaign.

The 52-year-old is married to Russian wife Ekaterina, also known as Katya, who drives a Range Rover with the British number plate MI5 SPY.

Her mother Olga Paderina, 68, said neither Katya nor Arron Banks had any business in Russia, dismissing claims her own husband Yevgeny had brokered a deal to plough money into the Brexit campaign.

The National Crime Agency launched a probe this week saying there were 'reasonable grounds to suspect' Mr Banks was not the true source of £8million of campaign funding.

Arron Banks with his wife Katya (centre) and mother-in-law Olga Paderina (right), on Olga's 65th birthday celebration in Yekaterinburg, Russia, 2015

Olga Paderina said her daughter 'flies the Russian flag high' and revealed Banks's children have Russian as well as British passports.

She said: 'It only amuses us and all our acquaintances. 'My daughter purposefully attached a SPY plate to her car. Just let them be afraid!'

'I know that neither Katya (Ekaterina), nor her husband have business here,' Olga - the 'babushka' or grandmother of Banks's children - said in another interview.

Referring to the Russian money rumours that have hit Banks, she said: 'How should you take it that somebody is building a sensation or a political campaign at your expense?

'I don't even defend my daughter - why should I if she is innocent?

'This Russian trace story comes from the West where it's pulled by the head and ears in any direction at all.'

Her husband Yevgeny has been described previously on a certificate for Ekaterina's earlier marriage in Britain as 'head of government property' in industrial Yekaterinburg, the family's home city.

But in fact he did not occupy such an elevated role before his retirement around a decade ago, the family said.

'My husband worked in the Property Fund 20 years ago,' former school director Olga told Ural news outlet ura.ru.

'He is an elderly man, he retired ages ago. Of course he doesn't have such power.'

Olga Paderina said her daughter Katya (pictured together) 'flies the Russian flag high' and revealed Banks's children have Russian as well as British passports

The 52-year-old tycoon Banks is married to Russian wife Ekaterina (pictured), also known as Katya, who drives a Range Rover with the British number plate MI5 SPY

Later he worked as head of an organisation training oil inspectors, say the family. 'He was not into financial wheeling and dealing,' insisted a source in the city.

She also revealed that the Banks' children speak 'perfect Russian' - and have Russian passports.

'My daughter has even been over to see us recently,' she said.

'This time she came over by herself, but before she was often here with children. All our grandchildren have Russian passports. They don't forget Russia.

'And my daughter proudly flies the Russian flag high. She is not embarrassed by her citizenship, her education or her roots.'

She has marched with her mother on a Victory Day parade in Russia held each May commemorating those who fell in the Second World War.

Meanwhile, mystery has emerged over Banks' suspected Kremlin links amid claims he made a previously unknown visit to Russia in February 2016 during the run-up to the Brexit referendum.

He was quoted as saying: 'My wife is Russian and we went on a family trip to Moscow, no meetings were had with anyone, we visited the Hermitage Museum and went on a river cruise.'

As the first picture emerged of the insurance tycoon in Russia - with his wife Ekaterina and mother in law Olga Paderina - there are questions over this 'family trip' claim.

First, the world famous Hermitage Museum is in St Petersburg not Moscow.

Banks's wife has marched with her mother on a Victory Day parade in Russia (pictured) held each May commemorating those who fell in the Second World War

In 1998 Ekaterina Paderina wed her first husband Eric Butler (pictured together), a retired merchant seaman, with whom she had one son

Second, river cruises do not run in February in either city due to winter ice. They usually in April.

The alleged trip emerged in leaked emails in June that Banks has hidden links to the Kremlin and its high profile ambassador in London, Alexander Yakovenko.

It is also believed Banks had travelled with his wife to Ekaterinburg - her home city - some months earlier in 2015 to mark his mother-in-law Olga 65th birthday.

This is when the picture with Ekaterina and Olga was taken, it is understood.

A family source indicated this was his most recent trip to see them in Ekaterinburg, although he had been a number of times previously.

Banks and his wife are believed to have met at a Britney Spears concert in London around 18 years ago.

A Russian school friend said she had long wanted to move abroad.

'She was considered attractive at school, and knew English really well,' he said.

In Britain she was a marketing student at Portsmouth University when in November 1998 she wed her first husband Eric Butler, a retired merchant seaman, with whom she had one son.

Arron Banks arrived back into Gatwick Airport this morning less than 48 hours after it emerged the National Crime Agency had launched a criminal investigations into donations he made

Banks and his wife (pictured) are believed to have met at a Britney Spears concert in London around 18 years ago. A Russian school friend said she had long wanted to move abroad.

Ekaterina Paderina at her wedding to Butler who was quoted last year by The Sunday Times saying he was quizzed by Special Branch over his bride

At the time he was 54 and she was 25.

Butler was quoted last year by The Sunday Times saying he was quizzed by Special Branch over his bride.

'They contacted me about two days after we got married,' he said. 'I was told to go to immigration to be interviewed for sham marriage.

'I said, 'It's not sham on my part'. The officer said, 'Don't you think the honey jar was presented to you because you are not the brightest bloke?'

The marriage ended the following year in acrimony and Ekaterina turned to controversial MP Mike Hancock who helped her remain in Britain and get a council flat.

At the time the Liberal Democrat was chairman of the all-party Russia group and a member of the Commons select committee on defence.

MI5 was later reported to be worried the Kremlin was interested in the MP's access to documents and Westminster contacts.

Ekaterina married Banks in 2001 and the couple have a daughter and a son.

Last year it was reported her email address included the numbers 007 and that she drove a Range Rover with the number plate MI5 SPY.