Train drivers at London North Eastern Railway (LNER) are set to strike every weekend in September, October and two in November, a union has announced.
The fresh strike action is separate to an ongoing pay dispute with all train companies, which edged closer to being resolved in England this week after a new pay offer.
Aslef, which represents train drivers, said the walkouts at LNER were due to a breakdown in industrial relations and agreements.
LNER operates services on the East Coast Mainline between London and Edinburgh and is run by the government.