The broadcasting and telecoms regulator said it was concerned Virgin Media could be putting "unnecessary barriers" in the way of people wanting to end their deals.
Ofcom has been told of customers being put on hold for long periods, their call being dropped part-way through the process, or requests even being ignored and customers having to make repeated calls to action requests.
NimbleFins previously reported Virgin Media was the worst paid-for TV service for complaints, compared with BT, TalkTalk and Sky. It also had above-average complaints for broadband, landline and pay-monthly mobile contracts.
Virgin Media said complaints about 'difficulties leaving' had halved over the last year. But Ofcom said being able to switch providers was crucial during the cost of living crisis as customers could save "hundreds of pounds" by changing deals.
The investigation comes as Ofcom also presses telecoms providers to introduce social tariffs "as soon as possible" to help those on low incomes access cheap broadband and mobile phone deals.
As NimbleFins explains here, social tariffs could save users £200 a year. Only 5% of those eligible – including those on benefits like Universal Credit - were signed up to one in April.
And now Ofcom is summoning providers to update it on progress in providing social tariffs. It will name and shame providers by publishing take-up of the deals in its annual pricing trends report later this year, to ensure enough is being done to raise awareness.
Ofcom chief executive Dame Melanie Dawes said: "Our rules are there to protect people and make sure consumers can take advantage of cheaper deals that are on offer. That's particularly important at the moment as households look for ways to keep their bills down.
"We're taking action today, on behalf of Virgin Media's customers, to investigate whether the company is putting unnecessary barriers in the way of those who want to switch away.
"We're also expecting more from the industry as a whole in helping to support customers through the cost-of-living crisis. That means no more excuses when it comes to offering and promoting social tariffs to eligible customers who could switch and save today."
A Virgin Media spokesperson said: "We are committed to providing our customers with excellent service, supporting them with any issues and giving clear options should they wish to leave.
"Complaint rates relating to 'difficulties leaving' have halved over the past year, showing the progress we're making, and we will keep working with Ofcom throughout its investigation, while making further improvements in how we handle customer complaints to provide a better overall experience."
Image courtesy of iStock.com / Peter Fleming.