High-street banks were last week warned they would be reported to the regulator if more evidence emerges of cautious consumers being mis-sold risky investment products.

More than 300 people have complained to the Financial Ombudsman Service (FOS) in the past two months alone over alleged mis-selling of high-risk financial products by branch-based bank staff, The Sunday Times can reveal.

The FOS is monitoring the situation closely. “With interest rates so low, people have been persuaded that this is ‘low-risk’, but as time goes by it becomes clear that this isn’t the case,” it said. “Where we start seeing enough cases that point to systemic problems — either with an individual firm or the type of product or sales approach — that’s something we would have to raise with the regulator. We’re keeping a close eye on this.”

The Money section has been inundated with stories from readers who are taking their cases to the ombudsman. Many complaints relate to banks that are now backed by the state — raising the prospect of the government facing multi-million-pound mis-selling claims for poor advice.

It’s not just government-owned banks in the firing line, though: the bulk of readers’ complaints relate to Barclays. It increased the risk ratings of a string of investment funds — without informing consumers.

One former Barclays worker said: “This kind of selling is fairly endemic in the banks — if people earn commission on products, then they’re going to sell products. Barclays is particularly product-focused, though — that was one of the reasons I left. It has more in-house products than other banks.”

Here we reveal some of our readers’ complaints.

Halifax

Susan Farrington sought the help of an adviser at her local Halifax branch when five years ago, at the age of 52, she was widowed and moved back to Britain from Australia. She had a lump sum of £40,000 to put away — money built up over years of saving — and didn’t want to risk her capital.

The bank, taken over by Lloyds this year and partly government-owned, recommended she put the money into its corporate-bond fund.

It now has a yield of more than 7%, but has lost 13% in the past 12 months and 17% over three years, against losses of 7.5% and 10% for the sector. Farrington lost about £10,000.

“Overwhelmed with the trauma of my husband’s death, plus the responsibilities that faced me, I went to numerous financial advisers for ‘expert’ advice to secure my future,” she said.