Eight hundred rail workers are to stage two one-day strikes and disrupt services across East Anglia in protest at the dismissal of a guard.
The strike action will hit train services across East Anglia
Rail, Maritime and Transport (RMT) union members at One Railways will walk out on 15 and 17 September.
Lines in Essex, Suffolk, Norfolk, Herts and Cambridgeshire will be affected.
One Railways said it was disappointed the RMT intended to proceed but was still keen to talk with the union in a bid to avert industrial action.
"We believe we have comprehensively and satisfactorily responded to the concerns raised by the union on safety and security and that industrial action is unnecessary," a spokeswoman said.
"It should also be noted that less than 38% of the RMT's 805 members at One Railways voted in favour of strike action.
"We expect to run a normal service on the West Anglia, Stansted Express and Metro routes, as well as on mainline services to Clacton, Braintree and Harwich."
The protest is in support of guard Paul Yarwood who was sacked after an alleged incident involving a fare evader.
Rail staff have also refused to sell advance tickets for the two strike dates.
In a ballot held last month, RMT members voted 300 to 59 to strike, saying the company had also neglected staff safety.
Bob Crow, of the RMT, said: "It is astonishing that the company still seems to have its head buried in the sand, not least because of the huge support that Paul has had from members of the public.
"Our members will be leafleting passengers during the strike to explain that the company's bizarre stance has left us no option but to strike again, this time right across the company."
Mr Yarwood, 45, of Brightlingsea, Essex, has been charged with using threatening behaviour following an incident at Colchester North Station, in Essex, in June.
He has appeared before Colchester Magistrates, where he denied the charge.
On strike days One Railways expect to operate an hourly service on the Norwich - London intercity services with some extra peak services instead of the usual half hourly service.
Local services from Ipswich and Norwich across Suffolk, Norfolk and Cambridgeshire are all unlikely to operate.
Southend - London services may experience some cancellations but it is hoped most services will operate.