Virgin Media is the UK’s most complained about broadband provider according to the latest figures, compounding woes for the firm, which is already under investigation by the communications regulator.

Figures released by Ofcom on Thursday showed that the number of complaints made about Virgin’s internet services between July and September were nearly double that of the next-most complained about provider, with Virgin attracting about 32 complaints per 100,000 customers compared with 18 for Now Broadband.

There was a general rise across the board, with a “significant” increase in complaints to Virgin across all of its broadband, landline and pay-TV services compared with the previous three months, Ofcom said.

A Virgin spokesperson blamed the latest rise in complaints on the fact that Ofcom had launched a formal investigation into the company in July, saying it had “generated a higher number of complaints than would ordinarily be expected”.

Ofcom launched the investigation after customers said they were having difficulties cancelling contracts and were unhappy with how the firm handled complaints.

“It should be noted that overall complaints about Virgin Media and O2 products still represent a very small proportion of our customer base,” Virgin said.

Fergal Farragher, Ofcom’s consumer protection director, said the regulator acknowledged the impact the investigation had had on complaints, but were “also aware that our investigation was in part based on complaints that customers had already made about Virgin Media’s services. We may publish updates on the investigation on our enforcement bulletin as the investigation progresses.”

O2, meanwhile, emerged as the most complained about pay-monthly mobile provider, with customers concerned about how their complaints had been handled.

It contributed to an overall rise in complaints across the sector, which Ofcom said showed that “providers must continue to focus on improving customer service”.

Sky generated the fewest complaints from both its broadband and landline customers.

Virgin Media said: “Our number-one priority is to provide an excellent service to our customers, and we accept that the rise in complaints in the third quarter falls far short of our expectations.

“As well as engaging fully with Ofcom’s ongoing investigation, we are investing in every area of our business to give our customers the best possible experience, with a real focus on resolving any issues at the first time of getting in touch and making it easier for them to get support when they need it.”