Can an employer withdraw a job offer on receipt of a poor reference?

Yes, provided that the job offer is conditional on receipt of satisfactory references, the employer can withdraw the offer if it receives a poor reference, without this amounting to a breach of contract.

An employer that receives a poor reference may wish to investigate the situation further to satisfy itself that the individual is unsuitable and that it does not wish to employ them. If the employer decides to go ahead with the employment, it can make it clear to the employee that continued employment is subject to the satisfactory completion of a probationary period.