You’re only a rich Brit once you’ve got $17 million

How do you know when you're rich? According to a survey out on Wednesday, most Britons reckon it is when you are worth over £10 million ($17 million).

Fifty-five percent of the 500 surveyed online by wealth advisory firm Oracle Capital Group said a personal fortune of over £10 million was considered rich – and around 200 people thought at least £100 million was required.

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Oracle said the survey proved the term millionaire no longer carried the cachet it once did.

"Many people who own properties in the London area have become millionaires by virtue of the dramatic inflation of house prices, but would not necessarily regard themselves as HNWIs (high net worth individuals)," said Yury Gantman, CEO of Oracle Capital Group, in a news release.

"This is undoubtedly a reflection of growing living costs which, alongside the housing market, have affected food prices, school fees, travel and other household outgoings, but also – as indicated by our survey – because their own personal assets are dwarfed by the immense and highly publicized fortunes of footballers, film stars, hedge fund managers and tech billionaires."

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Two-third of respondents – all of whom were U.K.-based – said the high visibility of celebrities had skewed perceptions of wealth. Most attributed this to the earnings of sports stars, but others highlighted the salaries commanded by those in business and finance, the media, and technology start-ups like Facebook, WhatsApp and Twitter.

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"What is clear is that the word 'millionaire' does not necessarily now conjure up the sense of significant wealth that it did until relatively recently; today, perhaps it's more about being a 'decamillionaire'," said Gantman.

Correction: This story was updated to reflect that 500 people were surveyed, in response to clarification from Oracle Capital Group.

—By CNBC's Katy Barnato. Follow her on Twitter: @KatyBarnato