Thousands of Virgin Media O2 staff face redundancy risk as the telecoms firm looks to save money in the face of billions of pounds of debt and tougher competition.

The broadband provider has not finalised the number of roles to be cut but it is likely be a sizeable chunk of its 16,000 workforce, the BBC understands.

VMO2 has billions of debt on its balance sheet and is tackling competition from both smaller providers as well as giants like BT, which has agreed a deal to acquire rival TalkTalk, a move which VMO2 has firmly opposed.

VMO2 declined to comment. The Prospect union, which represents VMO2 staff, said the cuts were “disappointing and very unsettling”.

Deputy general secretary Noel McClean said it is “committed to supporting our members through what is a difficult time, as well as also working with employers to explore ways to mitigate the number of redundancies and ensure retraining and redeployment of staff affected”.

The majority of the affected staff will be in non-customer facing roles and a number of senior leadership changes are already under way, the BBC has been told.

VMO2 is also expected to review its use of contractors and suppliers in conjunction with the job cuts that were first reported by Sky News.

As of 30 June, VMO2’s total debt stands at £27.2bn while it holds assets worth £45.9bn, according to the firm’s latest accounts.

Meanwhile, the company is dealing with fierce competition from cheaper “altnets” like Hyperoptic, Community Fibre, Gigaclear, and YouFibre.

VMO2’s had attempted to respond to this growing threat by buying altnet competitor Netomnia for £2bn via nexfibre, a joint venture owned by VMO2’s owners.

However, the Competition Markets Authority (CMA) has provisionally found competition concerns in the deal, external, with a final decision to come in December, sparking anger from VMO2.

At the time, VMO2 called the BT takeover a “stitch-up”, which allowed its rival “tighten its grip” over the market.

BT said its deal provided “a safety net” for TalkTalk customers as their broadband provider faced collapse without the takeover.

On Friday, BT’s share price jumped 7% after the Financial Times reported VMO2 was close to agreeing a deal , external to use its rival’s fibre broadband network.

VMO2 was minded to go ahead with the plans after halting upgrades and expansion of its own infrastructure to ease concerns over its debt pile, the paper reported.

The BBC has been told the deal is very close and that VMO2 is highly likely to announce it will stop all investment in fibre in its results on Tuesday.

Additional reporting by Ben King