Viewers tuning in to The Last Night Of The Proms could be left watching "dark screens" if proposed strike action goes ahead, a union said today.
The concert at the Royal Albert Hall in central London, which is famous for its traditional rousing chorus of Land Of Hope And Glory, is due to be shown live on BBC1 and BBC2 on September 11.
Broadcasting union Bectu sent out ballot papers to its 5,000 members at the corporation yesterday asking them if they were prepared to strike in a dispute over pensions.
If they vote to take action the proms show and other live events, including coverage of party political conferences, could be hit.
Luke Crawley, assistant general secretary of Bectu, said: "People at the BBC very rarely go on strike and with many shows being pre-recorded all that is needed is a manager to press a button to transmit it.
"But it seems to me that this time there could be an impact and there may be dark screens.
"Anything live would be hard for the BBC to do because you can't pre-record a live event."
At the moment, the corporation plans to broadcast the concert live on BBC Radio 3 and show the first half live on BBC2 and the second half on BBC1.
A BBC spokeswoman said: "We continue to believe that the proposals we are making will deliver a pension scheme that is sustainable, affordable and flexible for BBC staff and the Licence Fee Payer.
"We know that staff have concerns about the proposed changes but we will continue to listen and try to address these during the 90-day consultation period."
The BBC's coverage of the event, which dates back to 1895, is due to be presented by newsreader Katie Derham.