The Financial Conduct Authority (FCA) has warned investors about a firm that appears to imply it is regulated by using the name Vanguard.
Vanguard Asset Management is not registered and is attempting to clone the FCA-registered firm of the same name.
The clone firm has registered wesbite Vanguardassetmanagement.co.uk.
The website of the properly authorised and regulated firm is Vanguard.co.uk.
The unregulated firm claims an address at 25 Walbrook, in the City of London. The regulated firm has an address at 4th Floor, The Walbrook Building, 25 Walbrook, in the City of London.
A spokesman for the FCA said: "Almost all firms and individuals carrying out financial services activities in the UK have to be authorised or registered by us.
"This firm is not authorised or registered by us but has been targeting people in the UK, claiming to be an authorised firm.
"This is what we call a 'clone firm'; and fraudsters usually use this tactic when contacting people out of the blue, so you should be especially wary if you have been cold called. They may use the name of the genuine firm, the 'firm reference number' (FRN) we have given the authorised firm or other details."
Vanguard sparked a price war last year with the launch of a direct-to-consumer online investment service, charging an annual account fee of just 0.15 per cent.
The service required a minimum lump sum investment of £500 or a minimum monthly contribution of £100.
There is no account fee above the first £250,000 invested, meaning this fee is effectively capped at £375 a year.
On top of this investors are charged an ongoing charge for the funds, which across Vanguard’s proposition averages out at just 0.14 per cent.
Ryan Barrows, head of personal investing for Vanguard, said charges for the service could come down even further if it proves popular enough.
He said: "We are quite proud of the fact the vast majority will pay less than 40 basis points all in.
"As we continue to grow here, we fully anticipate we would give our investors the benefits of that scale."