Which? said it has written to bosses at Virgin Media, Scottish Power and British Gas over their poor customer service.

The consumer champion urged chief executives Lutz Schuler, Keith Anderson and Chris O’Shea to ensure improvements to their firms’ “consistently poor performance” after recent research found them to be the worst scorers.

The watchdog surveyed 4,101 people in May on issues like how long it took to get in touch with someone who could help, the variety of contact options, how seriously the customer service representative took the issue and how well the issue was resolved.

The Yonder poll found that energy and broadband remained two of the worst performing sectors – with net satisfaction in customer service interactions in energy and broadband at plus 51 and plus 52 respectively.

Rocio Concha, Which? director of policy and advocacy, said the watchdog is calling on the firms “to give consumers the customer service they deserve and clearly communicate the steps they are taking to improve”.

Virgin Media was identified as the worst performing broadband firm, receiving plus 29 for overall customer service – significantly lower than the sector average of plus 52.

Half (50%) of Virgin Media customers experienced at least one customer service issue, which included waiting a long time on the phone to speak to an adviser (51%), being passed between departments without a helpful response (36%) and speaking to unhelpful or dismissive advisers (34%).

Meanwhile, Scottish Power and British Gas remained the worst performing energy firms, receiving plus 34 and plus 43 respectively for overall customer service, the survey found.

Both firms’ scores improved since Which? last looked into this area, the consumer watchdog said, noting that the firms are investing in their customer service.

But Scottish Power still came bottom across the board and British Gas received scores well below the sector average of plus 51 for overall customer service.

More than half (55%) of Scottish Power and half (50%) of British Gas customers said they had experienced at least one customer service issue in the last year.

Ms Concha said: “Our research lays bare the dire state of customer service – with some companies simply not up to scratch.

“Virgin Media, Scottish Power and British Gas remained the worst performing broadband and energy firms for customer service.

“It is never okay for firms to provide sub-standard customer service, but in essential sectors providing vital services millions rely on every day such as energy and broadband, it is completely unacceptable.”

A Virgin Media spokesperson said: “We are making real changes across our business to deliver customer service improvements and we’re already seeing tangible results that wouldn’t be reflected in this old survey from Which? that, incidentally, represents less than 0.01% of our customer base.

“We have boosted the number of agents, including in specialist teams that handle the most complex issues, and are investing more money in customer-facing areas of the business. We’re also multi-skilling our teams, transforming our IT systems and improving our digital tools, including through new technology that will solve customers’ issues even before they report a fault.

“While change can take time, this programme of targeted investment has already seen us reduce average call waiting times to just two minutes, and last year 95% of customer complaints were resolved first time. We’re continuing to focus on removing pain points and delivering the best possible service to our customers.”

A spokesperson for Scottish Power said: “We service 2.9 million customers a year across a range of channels, including phone, chat, email and online. 97% of customer emails were responded to within two days and our average speed of answering phone inquiries is under 107 seconds.

“These figures, published as part of a much larger and more robust study by Citizens Advice are more representative than the 217 customers (0.007% of our customer base) surveyed by Which? and puts us top of the large suppliers when it comes to customer service call waiting times and email turnaround.

“We’ve worked tirelessly to improve and enhance our services for all of our customers and will continue to do everything we can to help them.”

A British Gas spokesperson said: “The survey is not representative. Out of 4,101 respondents it included less than 500 of our customers and is based on data that is up to a year old.

“We’ve invested £50m in our customer operations since the start of the energy crisis – this includes hiring 700 more UK-based contact centre staff at the end of last year, introducing longer call centre opening times and providing additional training to our dedicated colleagues on supporting customers in financial difficulty.

“This investment is working, customers are seeing a difference, that’s why as part of the trusted Uswitch Energy Awards last month we received recognition for best overall improvement. We’ll continue to look at how we can further improve customer service.”