SCOTTISHPower are one of the three most dreaded call centres in Britain, new research reveals.

Consumer watchdog Which? say the Glasgow-based company ranks bottom of both the gas and electricity providers study on customer satisfaction. Bank of Scotland are ranked lowest in their banking results.

Which? asked more than 7,000 consumers to rank the companies in their satisfaction survey based on staff knowledge, phone menu system, politeness, helpfulness and waiting times.

Consumers were most frustrated with broadband and energy providers, who ranked the worst overall for their long waiting times, poor staff knowledge and lengthy phone menus.

Last week a Citizens Advice report said that ScottishPower received the highest number of complaints ever recorded for a UK energy company in a quarter.

There were 1,163 complaints about Scottish Power per 100,000 customers in the last quarter of last year, the national charity and consumer advocate said.

It is the highest figure ever recorded against a single supplier, ending a year in which the total number of complaints about the Big Six provider increased by 488 per cent, the figures show.

The Spanish-owned company was banned from proactive sales for 12 days in March after failing to meet customer service targets set by Ofgem.

ScottishPower joined BT and TalkTalk as the only three companies to score an overall rating of just one star out of five in the new Which? research.

The poll found only just over half of broadband providers (58 per cent) answered calls in the first five minutes, compared with 89 per cent of car insurers and 83 per cent of banks.

Around one in 10 customers (12 per cent) felt the person they spoke to at their energy provider had poor or very poor product knowledge, a belief shared by 17 per cent of callers to broadband companies.

A third of BT Broadband customers (34 per cent) rated its customer service as poor or very poor, while 21 per cent of Scottish Power electricity customers had spent more than 20 minutes waiting for an answer in the last six months.

Almost a fifth (18 per cent) of npower's electricity customers thought staff knowledge of its products and services was poor or very poor.

In contrast Ovo Energy, NFU Mutual, Zen Internet and First Direct all scored five stars across the board.

Almost all those surveyed (95 per cent) said calls should be answered within five minutes by a human voice, not an automated service, and 90 per cent said UK companies should operate UK call centres.

Which? executive director Richard Lloyd said: "Unfortunately, poor customer service from call centres has become a 21st century bug-bear for too many people.

"Customers should vote with their feet if they're tired of waiting or fed up with the service they get.

"We want the worst offenders in our survey to raise their game by answering the phone quicker and improving staff training to demonstrate they really value their customers' time."

A ScottishPower spokesman said: "We had a very challenging period following the introduction of a new £200 million customer IT system, and we apologise to any customers who experienced issues. Major improvements have been made recently and our call response times have improved significantly since this survey was undertaken. In April 2015, customer calls were answered in 60 seconds on average and this is one of the best levels in the industry. Our call centre opening hours are also the longest in the industry."