Lloyds Banking Group is engaged in a new and unpublicised review of the mis-selling of 'guaranteed' and 'capital protected' bonds, the so-called structured products which were heavily sold by all the high street banks until recently.

Lloyds, headed by Antonio Horta-Osorio, who accepted a controversial £1.5 million bonus last year, was selling its Scottish Widows bonds right up until 2012 when, like other banks, it withdrew from selling investments in branches to most customers ahead of the outlawing of commission payments last December.

Structured product sales typically earned banking 'advisers' high levels of commission.

Now Lloyds is reviewing a limited sample of sales of three Scottish Widows products, including the Capital Protected Fund 5, the Protected Capital Solutions Fund, and the Guaranteed Investment Bond, typically sold in 2007 when the FTSE-100 was above 6000.

Structured products typically safeguard capital but need a chosen index to be higher after five or six years to deliver any returns.

Only two years earlier, in 2005, Lloyds was fined £1.9m by the Financial Services Authority for mis-selling the Scottish Widows Extra Income & Growth Plan, which did not guarantee capital, to 22,500 of the 51,000 investors who had been sold it in the previous two years.

The latest Lloyds review follows the submission to the bank of a dossier of mis-selling complaints by a newspaper, which said it suggested there had been widespread mis-selling in branches to customers in their sixties and seventies. It said they had been promised 100% capital protection, but also returns of up to 75%, which had not materialised.

The bank this week admitted 25% of the complaints were justified, and said it was conducting a "full review" – but only of the small number of cases submitted.

More than 40,000 of the three types of bond are understood to have matured in the past year.

Asked yesterday whether Lloyds would now review all its sales of the bonds, a bank source said it had "decided to look at certain specific customer groups", adding: "We will consider our next steps following the review of these cases."

The bank did not agree that structured products were widely mis-sold by branch advisers, and the complaints upheld had been in a minority.

The Herald highlighted last month that on April 1 Lloyds Banking Group moved its advisers onto a non-sales-based reward system for the first time.

A bank spokeswoman said there was "no connection" between that and the complaints, adding: "We review our schemes on a quarterly basis and have made significant changes since the start of 2012."