Using agency workers during a strike: the legal position

As the CWU seeks legal advice on whether it can take Royal Mail to court over its use of agency workers during the postal strike, employers may be concerned about what contingency plans they can use if industrial action goes ahead.

Law firm Pinsent Masons has said that it is possible for employers to use an employment agency to supply workers and employ them directly to cover for striking employees, as long as they are employed directly by the firm and not by the agency supplying the workers.

Here is a brief guide from Pinsent Masons, outlining how far employers can go to ensure minimum disruption to business during strikes.

What an employer can do

Use an employment agency (a firm that does not itself employ the workers whose services it supplies to the end user) to supply workers and employ them directly:



  • An employment agency can lawfully supply workers for the employer to employ directly at any time. The agency could even do the pre-recruitment screening.
  • It follows that the employer can make use of the services of such an agency without aiding and abetting any criminal offence by the agency, since none would exist.
  • An employer can move existing employees from other parts of the business (or group) to cover for striking employees: this might be inflammatory but is not unlawful.
  • These employees might be workers recruited via an employment agency but employed directly by the business, but they must not be ‘agency workers’.
  • Employers can continue to use any agency workers already supplied on a ‘business as usual basis’ for the original purposes for which they were engaged. They should not, however, be specifically re-allocated to the duties normally performed by colleagues taking part in industrial action.
  • Any agency worker already supplied who leaves can be replaced by another agency worker who should only perform the work for which their predecessor was engaged.
  • Agency workers can be used for duties relating to the business, even if indirectly relating to the industrial action, as long as they are not actually covering for employees who are taking part in the industrial action.

What an employer cannot do



  • Use an employment business (a firm that employs the workers whose services are supplied to the end user) to supply their own employees if this is to replace an employee who is taking part in either a strike or industrial action short of a strike. Regulation 7 states that it would be an offence for an employment business to supply an agency worker specifically to carry out:

    • “the duties normally performed by an employee who is actually taking part in a strike or other industrial action
    • the duties normally performed by an employee who is covering the work of a worker who is taking part in a strike or other industrial action… unless the employment business does not know, and has no reasonable grounds for knowing that the employee is taking part in a strike or other industrial action”.

If the employment business is guilty of an offence under the regulations, the end user can be guilty of aiding and abetting that offence.

The Pinsent Masons guide said: “It is important to note that the 2004 Regulations prohibit employment agencies from doing certain things. Therefore, the offence [of using agency workers during strikes] would be committed by the agency. The employer would be guilty of ‘only’ aiding or abetting the agency’s offence.

“A key distinction in the 2004 Regulations is between an employment agency (EA) and an employment business (EB). An EA does not itself employ the workers whose services it supplies to the end user; by contrast, an EB does employ the workers whose services are supplied to the end user.”

Royal Mail is currently in talks with CWU to try and avert further strikes. Umbrella union body the TUC has got involved to help resolve the dispute over pay and job cuts.

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