PPI now accounts for 13 per cent of all nuisance calls, down from 22 per cent in 2013, although it remains the most common type of unwanted call, Ofcom said.

Nuisance calls about home or loft insulation rose, solar panels and other products related to home improvements increased.

The study also found the number of people receiving unwanted calls, and the average number received, remained broadly unchanged year-on-year.

The most prevalent types of nuisance calls were live marketing calls, which made up 38 per cent of all unwanted calls, followed by silent calls (37 per cent) and recorded sales calls (12 per cent).

Ofcom said it continues to pursue a number of companies suspected of making silent and abandoned calls. Most recently, an investigation was opened into Ageas 50 Limited, trading as RIAS and Castle Cover.

In the first quarter of this year, the regulator said it had taken informal action against 20 companies. As a result, complaints about telephone numbers used by nine of these have stopped, while complaints have fallen significantly for four.

Ofcom is also reviewing its silent and abandoned calls guidelines. The review will explore whether there is scope for strengthening these and will look at any relevant developments in call centres’ practices and technology.

Claudio Pollack, Ofcom’s Consumer Group Director, said: “While progress is being made, we are under no illusions that there is still more work to do. Together with Government, other regulators, consumer groups and charities, we’re exploring all possible ways of better protecting consumers.”

Ernest Doku, telecoms expert at comparison site uSwitch.com, said: “Unwanted calls are a modern day scourge that is clearly showing no sign of abating, as Ofcom’s research reveals.

“At the very least unwanted calls are annoying, and at the most they are distressing for vulnerable people who can’t understand why they are being hounded.”

Ofcom has published new guides to help consumers prevent nuisance calls.