Were there any other employees let go who might be in the same situation? Could you pool resources with them?
Have you tried contacting the directors directly. They have ultimate responsibility for the affairs of the company.
You should send a registered letter telling the employer that unless you get the appropriate documentation within 7 days, you will be reporting them to the Revenue Investigation Unit on suspicion of revenue fraud.
Whether this works or not, you should report them.
When you say "the accountant", so you mean an employee of the company or an auditor or external accountant? If they are qualified, then you should complain them to their Institute. You will be told that they can't intervene, but they will probably refer the question to her.
Brendan