Prudential Assurance received 330 new complaints between January and June, up 7 per cent on last year’s first half, and of which 17 per cent were upheld.

The firm was closely followed by Phoenix Life, which was complained about 327 times – also up 2 per cent on the last six months – but whose uphold rate was slightly higher, at 23 per cent.

Aviva came at number three, followed by Royal London and Sun Life – although all three received fewer complaints than in the same period last year.

Sun Life had the highest uphold rate at 27 per cent.

The investment complaints space was dominated by the five major banks – Lloyds TSB, Barclays, Santander, HSBC, and Bank of Scotland – although all five have seen a fall in complaint volume on H1 2013.

Barclays’ uphold rate was highest at 57 per cent.

While mortgage gripes were also largely attributed to the banks – mainly Bank of Scotland, Santander, and Barclays – Legal & General (L&G) posted a noteworthy increase in complaints of 916 per cent on the previous six months and 760 per cent on the first half of last year.

The firm amassed 447 complaints in the period – considerably fewer than the Bank of Scotland’s 1,062, while its uphold rate was lowest of the five listed firms, at 11 per cent.

The FOS said the complaints are mainly to do with advice provided at the point of re-mortgage and are in the early stages of investigation.

L&G said last month it is considering launching lifetime mortgages as more retirees eye equity release to fund their income.

Overall, the most complained about business groups were the top banks, which all saw a fall on previous periods.

The FOS took on 191,129 new cases in total in the first half of 2014, 70 per cent of which were made up of payment protection insurance (PPI) claims.

For complaints about financial products other than PPI, the total number of cases referred to the ombudsman was 3 per cent higher than the second half of 2013 (57,310 compared to 55,747).

This included banking complaints increasing by 7 per cent and insurance cases by 1 per cent, the FOS said.

The average uphold rate over the period was 57 per cent, up from 51 per cent during the previous six months.

Chief ombudsman Caroline Wayman said: “Responsibility for sorting out the mass mis-sale of PPI is still the major part of the ombudsman’s workload. But during the first half of 2014 there’s been a marked change in the type of complaints consumers are asking us to resolve – as underlying attitudes become more entrenched and the issues involved get more complex.

“We’re hearing growing dissatisfaction from people about being processed industrially as a number rather than being listened to as an individual customer.

“By giving their customers more thoughtful, considerate and personal responses – clearly setting out the reasoning behind an individual decision – we know that businesses can help sort out problems earlier on, prevent complaints being escalated to the ombudsman and rebuild trust and confidence more generally.”