Which has urged the public to shop around for financial advice after its research found fees for the same client could vary by as much as 900 per cent.
In a survey of 108 financial advisers the cost of advice for a client with £100,000 in savings and a £150,000 pension varied between a minimum of £500 and £5,000 at the top-end.
The hypothetical client also had £100,000 in an investment Isa and was looking for advice on drawing an income on retirement, with the average quote for the service sitting at £2,540.
In light of the results Which warned it was "crucial" to shop around amid the "huge disparity" in what advisers charged for their work.
In another example advice fees varied by 733 per cent for a client who was 10 years into her career and looking to start saving for her child's university education.
With £60,000 in savings and £40,000 in an investment Isa, the minimum fee was £300, the average £1,060 and the maximum £2,500.
Of the advisers Which spoke to only one in six charged a flat fee, while an even smaller 6 per cent charged on an hourly basis.
The majority, 69 per cent, charged a proportion of the money they managed and the remainder charged a combination of hourly, fixed and percentage fees.
According to Which's annual member survey, a third of its members had taken financial advice and four in five of these had opted to use an IFA - the rest chose to use a restricted adviser.
Jenny Ross, Editor of Which Money, said: "There are a number of benefits to using a financial adviser, but it’s important to shop around to find the right adviser for your needs.
"Look for a personal match as well as a decent price, and don’t shy away from asking important questions when meeting with potential advisers.
"Before accepting any advice, make sure you understand what is being recommended to you, and that you’re happy with what’s on the table before proceeding."
Ms Ross also urged consumers to check their chosen adviser was authorised by the Financial Conduct Authority.
Ricky Chan, director at IFS Wealth & Pensions, said: “These fee comparisons usually miss out on a lot of key information, such as what’s included as part of the service, for example cashflow planning, reviewing underlying products and investment strategy, the location of the firm, whether the adviser and firm are Chartered Financial Planners and independent, whether implementation fees are on top of the advice report fees etc.
“I can say for certain that the £500 quoted is misleading and a huge anomaly, even if significant shortcuts are used.”
Mr Chan said charging a proportion of money managed was certainly the leading fee structure across financial advice firms.
He said: “This is because it is a rough proxy to factor in the complexity and risks involved in cases, and it is generally easier for clients to understand compared with a long menu of charges.