The company also warned that its dividends may be halved to deal with the cost of the claims.
The total dividend for 2023 has already been halved to 23.83p compared to the previous year.
The firm, one of the biggest wealth advisers in the UK with around 5,000 partners, said it had seen a string of complaints, many from complaints handling companies, that ongoing advice which should have been given to clients had not been provided to the level expected.
Last year the firm announced, in October, that it had concluded a "comprehensive review" of its client charging model and announced plans for a simpler and more comparable charging structure.
SJP has been attempting to repair and enhance its brand.
In March the firm entered into its first TV sponsorship deal as it aims to increase its brand awareness.
The wealth manager said its advertising campaign would promote the benefits of taking financial advice.
The cost of the sponsorship has not been disclosed.
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