Hundreds of Border Force officers at Heathrow will take industrial action for 23 days from the end of the month over a long-running dispute about changes to their terms of employment. About 650 members of the Public and Commercial Services (PCS) union will go on strike from 31 August to 3 September at which point a period of work to rule – where no overtime is undertaken and no extra work is done beyond what is contractually required – will begin and continue until 22 September. The PCS members who work in passport control at terminals 2, 3, 4 and 5 at Heathrow have been in dispute with their employer after a new roster was introduced in April. The union said about 160 staff have left the Border Force because of a lack of flexibility and changes to shifts, while others have been forced to change their working hours and practices. The PCS general secretary, Fran Heathcote, said: “Our hard-working members at Heathrow take great pride in keeping our country’s border safe, but many are being forced out of the job they love. “They are being told by managers to choose between caring responsibilities and their job, which is no choice at all. The only reason they’re being forced to choose is because their managers are forcing them. “We know our strike action is likely to cause serious disruption to travellers using Heathrow at the end of the summer, but the strike can be avoided if the employer listens to the concerns of our members.” The union added that women and those with caring responsibilities have been particularly affected by the changes, while new staff have been refused flexible working applications. Bosses at Heathrow, Europe’s largest airport, have said they will work closely with Border Force to support contingency measures during strike periods. PSC members have already taken seven days of industrial action in April, May and June as well as action short of a strike that included a work-to-rule and an overtime ban. In May, the Guardian reported that members of the armed forces were being trained to cover for striking Border Force staff at ports and airports. Dozens of uniformed soldiers were seen at Home Office facilities in south-east England. Emails showed that senior Border Force officials secured assistance from the Ministry of Defence to form a backup workforce. Sources said soldiers were being given training of less than a week so they could check passports and look out for signs of drug smuggling, people trafficking and modern slavery. The Home Office was contacted for comment.