This afternoon's NUJ and Bectu strike action has forced the BBC to cancel a number of flagship news programmes, including PM and Newsnight.
BBC journalists and technical staff are on strike in a row over jobs, workload and claims of bullying, threatening disruption to TV and radio programmes this afternoon.
Members of the National Union of Journalists and the technicians' union Bectu walked out from offices and studios across the UK at noon for 12 hours, and will follow the action with a work to rule.
A spokesperson told Press Gazette that while PM, Newsnight, the World Tonight and the World at One are expected to be cancelled, BBC One's news bulletins will not be disrupted and tomorrow's Today programme is expected to go ahead.
In addition, the Six O'Clock and Ten O'Clock News will go ahead on BBC One.
The BBC News channel is currently broadcasting only half of its material live.
The BBC has said it is "disappoined" by the action and issued an apology to viewers for the expected disruption.
A corporation statement said: "We have had constructive meetings with the Unions in recent weeks and whilst we’re unable to postpone planned compulsory redundancies for six months as they requested, we do agree that stress and workload are areas of real concern.
"If workloads are going up because of the pressures of working in a 24/7 digital media environment and implementing savings, it’s in everyone’s interest to understand the issues and work with individuals, their managers and the unions to address it.”
Unions will mount picket lines outside BBC centres, including New Broadcasting House in central London, warning that the action will hit the Bank Holiday schedule and will affect programmes including news bulletins.
The unions are protesting at the so-called delivering quality first (DQF) programme which will lead to 2,000 job losses. At last count the dispute centred around 30 proposed compulsory redundancies of journalists.
The BBC apologised for any disruption caused by the strike, but said it could not agree to union calls for compulsory job losses to be postponed.
Michelle Stanistreet, general secretary of the NUJ, said workers were sending a clear message to the BBC that it needed to address problems created by the "ill conceived and badly implemented" cuts.
She said: "It is disappointing that once again the BBC has decided not to properly engage, refusing our call for a moratorium to give space for meaningful discussions on the worrying impact of the cuts. The DQF plans remain on the table, regardless of the consequence for workload and stress levels.
"We know that the cuts are already having an impact on the quality of work. We know that it is leading to unacceptable workloads and stress. We know that management is using DQF as a means to harass and bully staff – making worse an already entrenched problem of bullying that has been largely ignored by those in positions of power."
Gerry Morrissey, general secretary of Bectu, said: "Our members are suffering because the BBC thinks it can deliver the same levels of output with many fewer staff. The reality is that excessive workloads caused by massive job cuts are already taking their toll with staff reporting more stress, more bullying and more harassment. The BBC has a duty of care which it is not exercising currently and it is great pity that strike action is needed to make senior managers take the issues seriously."
The unions said they are confident that the strike will be well supported, amid warnings that staff morale was at "rock bottom," and the NUJ and Bectu have called for a six-month moratorium on job cuts to allow for a review of workplace issues.
A BBC spokesman said: "We are extremely disappointed that the unions have gone ahead with the strike and apologise to our audiences for the disruption to services."