More than 5,000 civil servants who work in water safety and food controls are on strike today in a row over pay.
Employees at the Department for Environment, Food and Rural Affairs and other government agencies dealing with environment and agriculture will walk out in protest at the "widening" pay gap with other civil servants.
The Public and Commercial Services Union said some of its 5,500 members involved in the dispute earned £2,010 less than workers doing similar jobs.
Starting salaries across the agencies ranged from £11,400 to £15,200 for people doing the same type of work, according to the union.
Its general secretary, Mark Serwotka, said: "Defra and its executive agencies are a prime example of the unfair and farcical nature of civil service pay.
"Members doing the same job have had enough of the growing inequality of pay and want to see people doing the same job paid the same rate."
Workers will mount picket lines in several regions of England and Wales, including London, Exeter, Bristol, Newcastle and York.
