Many thanks for your patience. First of all there is no legal requirement on employers to issue a reference for a previous employee, even if it is a very simple factual reference confirming his dates of employment or job role. There will only be an obligation on the employer to do so if this was a contractual right, i.e. the contract they had stated that the employer must issue a reference in the future.
In the absence of a contractual obligation, there is no legal requirement on them to issue a reference at all, even if that means future employment opportunities may be jeopardised.
Saying that, if he had blown the whistle and the reason for their refusal to issue a reference is because of this, that could amount to detrimental treatment due to making a protected disclosure and be unlawful. I suppose the way to consider this is by looking at whether other employees who had not made a disclosure been given references and if he is the only one that has not been issued with one, then it could help the argument that it is done because of the whistleblowing. Whilst he cannot force the employer to issue a reference, he can consider a claim for detrimental treatment against them, or at least use this as a threat to get them to change their mind
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