These include slow broadband speeds, connection drop outs, outages and router problems. The findings come as the majority of broadband providers have increased prices this year, some by 14% or more.

Among the big providers the issues were consistent and there were very narrow margins between the best and worst offenders, said Which?, the group behind the research.

When it asked customers if they had experienced a performance issue, Sky had the lowest proportion who had not had a problem, at 32%. It was followed by Virgin Media and then EE with 35% and 37% respectively.

For those with Now, 44% said they had not experienced an issue and for Vodafone it was 46%. Plusnet was 47% and BT was 49%, the highest figure among the big providers.

Customers with Hyperoptic and Shell Energy Broadband were less likely to experience issues, with 52% saying they had not had a problem, followed by Utility Warehouse at 50%.

In Ofcom’s latest complaints data, Sky was on the the least-complained about providers, while Shell Energy had the highest number of complaints.

Connection drop outs and low broadband speeds

Frequent connection drop outs were the most common broadband issue of the 4,000 people asked with 19% affected followed by connection speed, impacting 17% of respondents.

Next it was slow uploads and downloads, affecting 15%, router problems impacting 14%, and 14% also said they had been left without a broadband connection for at least an hour. While 12% said they had experienced slow or disrupted streaming while listening to music or watching videos and 8% were left without a connection for a day or more.

When looking at broadband customer service, 44% said they had experienced an issue and 11% said they found it hard to get in touch with their provider or struggled to get an issue sorted.

The regulator Ofcom called for broadband providers to improve their customer service earlier this year, especially given the high price hikes which have been brought in. Providers were also given guidance by the Advertising Standards Agency (ASA) on how to describe price hikes to make sure customers can clearly understand how their bills may change.

The consumer group is now calling for providers to allow customers to leave without penalty if they face a mid-contract price hike. These are allowed, if written into the terms and conditions of a contract, but they mean many people may see their price hiked and not be able to switch away without paying a big penalty.

‘Completely unacceptable’

Rocio Concha, Which? director of policy and advocacy, said: “A reliable connection is essential to modern life.

“It’s completely unacceptable that customers who have faced these eye-watering increases are also experiencing so many problems with their connection. Broadband firms need to work harder to resolve these issues and offer a better service.

“While some customers are able to switch away to better service and prices, many are trapped in contracts where they either have to accept above inflation price hikes in the spring or pay exorbitant exit fees to leave the contract early. It’s absolutely critical that Ofcom’s review of inflation linked mid-contract hikes results in changes that ensure customers are never trapped in this situation again.”

What the providers said

An EE spokesperson said: “Ofcom’s latest complaints report shows that we remain one of the least complained about broadband providers, with complaints remaining well below the industry average throughout recent years.

“We remain committed to providing the best customer service across the industry and ensuring our customers get value for money as the UK’s best network. Our teams across the UK and Ireland already provide the most personal and local service in contact centres and retail stores across the country.

“We have proudly led the way with social tariffs since 2008, with around 80% of the total market being supported on BT social tariffs. Customers who are struggling financially and are eligible for our social tariffs can move penalty-free at any point in their contract, this also includes EE and Plusnet customers.

“Any customer worried about paying their bills should contact us and we will help find a solution which works for them.”

A Sky spokesperson said: “We are committed to providing the best service to our customers. We do not believe this is a representative survey – Ofcom’s quarterly complaints data shows we are consistently one of the least complained about broadband providers and, in Ofcom’s latest report, we received the fewest complaints out of all broadband providers.”

A Virgin Media spokesperson said: “While these findings are only taken from a small sample of customers, the latest, fuller data from Ofcom shows that our customers benefit from the fastest download speeds, and customer complaints on our broadband services fell by 22% in the first quarter of this year.

“Only last month we were rated the ‘Best in Test’ in Umlaut’s broadband benchmarking survey, ahead of other major providers.

“With demand for connectivity higher than ever, we’re investing billions of pounds each year to upgrade and improve our networks to ensure we’re providing our customers with fast and reliable broadband services they can rely on. Customers are receiving more value than ever from their telecoms services, and we continue to invest in every area of our business to ensure we continue to improve and deliver an excellent customer experience.”