Roxy and Ronnie Mitchell are to be killed off during the 'EastEnders' New Year's Eve special.
Actresses Rita Simons, 39, (Roxy) and Sam Womack, 43, (Ronnie) are said to be upset by the news because they'd hoped the door would be left open for them to return, while the other cast members are reported to have complained that they have not been consulted.
A source explained: ''Everyone's in shock. The cast are really upset as it's come out of the blue.''
The planned exits of Roxy and Ronnie have been instigated by new producer Sean O'Connor, who also recently killed off characters Margaret Midhurst and Paul Coker.
The source told The Sun on Sunday newspaper: ''People are worried who's going to be next. The script for Roxy and Ronnie's deaths has been written, but none of the actors know what's going to happen.''
Meanwhile, a spokesperson for the BBC has refused to comment on future plans, saying he does not wish to ruin the surprise element for fans of the show.
He said: ''We know how much our audience hate to have any future storylines spoilt so we will not comment on speculative stories.
''At no point have we received any concerns from cast about any of our future storylines.''
Roxy and Ronnie first joined the programme in 2007, when they were introduced as the cousins of Phil and Grant Mitchell.