Embattled rail passengers in Northampton look set to be hit again after train conductors last night announced plans to strike for a fourth time in a row over Sunday working.
Members of the Rail, Maritime and Transport Workers Union (RMT) will strike on Tuesday, April 14.
The union said London Midland had failed to give it assurances on the right to opt out of Sunday working and as a result 100 conductors based at depots in Northampton, Bletchley and Watford will strike.
A spokesman for London Midland said: "On Monday we ran around 80 per cent of our normal services. We are determined to run the fullest possible service on Tuesday. We thought a breakthrough had been made but sadly it seems the RMT is set on a course of disruptive action. We believe this is a historical issue. We are still prepared to sit down with the RMT."
RMT general secretary, Bob Crow, said: ""It is disappointing that after three rock-solid strikes London Midland has not recognised the depth of feeling of our members over the issue.
"The company knows we are available to talk, and we hope they will now do just that and settle this dispute on the basis of voluntary Sunday working."
A two-day strike took place on Sunday and Monday and two one-day strikes took place in March.