A rail union has announced strike action on two dates next month, adding to disruption already planned on the network.

The Transport Salaried Staffs' Association (TSSA) has agreed to strike on 18 and 20 August at seven train operating companies in an industry-wide dispute over pay, job security and conditions.

Staff will walk out at Avanti West Coast, c2c, East Midlands Railway, CrossCountry, Great Western Railway, LNER, and Southeastern.

Thousands of rail workers spanning station staff, operational, maintenance, supervisory and management staff, will take part in the strike.

This is the first rail industry-wide action taken by TSSA in more than a generation, the union said.

Some form of industrial action will take place on West Midlands Trains, Northern, Greater Anglia and TransPennine Express - but this will fall short of a full strike.

The action is being called over demands for greater pay, as well as concerns over the closure of ticket offices and "widespread job cuts" on railways.

The government has disputed a claim by the TSSA that some workers have had their pay frozen for four years.

And no final decision has been made about the closure of ticket offices, although on average only one out of eight tickets sold is purchased from a person.

The median pay of a railway worker increased by roughly 25% between 2011 and 2021, from £35,000 to £44,000, according to government statistics.

This compares to a national rise of 23%, from £21,000 to £26,000, across the country. The median is only one type of average, and describes the middle value of a range of numbers.

The RMT union had already announced strike action towards the end of July and in August.

Earlier this summer, an RMT walkout became the largest British rail strike in 30 years.

Manuel Cortes, the general secretary of TSSA, said: "The Tories' cost-of-living crisis is the worst in living memory. Essential items like food, energy and clothing costs are going through the roof yet the government has chosen to pick a political fight with rail workers.

He added: "The Conservative government is the clear block to a deal for rail workers. Grant Shapps must either personally come to the table or empower train operators to reach a deal on pay, job security and conditions.

"Instead of wanting to resolve this dispute, we now see proposals for hundreds of ticket office closures and widespread job cuts across our railways."

A spokesman for the Department of Transport said: "It's hugely disappointing that, rather than commit to serious dialogue with the industry, the TSSA is seeking to cause further misery to passengers by cynically coordinating strikes to cause maximum disruption to the rail network.

"Our railway is in desperate need of modernisation to make it work better for passengers and be financially sustainable for the long term.

"The only thing more strikes will do, however, is wreak further havoc on the very people unions claim to stand up for - people who, on average, stumped up £600 per household to keep our railways running throughout the pandemic while ensuring not a single worker lost their job.

"We urge the TSSA to reconsider and work with its employers, not against them, to agree a new way forward."