You collect the evidences of the fraudulent activities of the said companies using your company's name as their internal auditors.
If possible you may even collect their account details with signatures of the auditors.
Then you may inform the ROC and also issue a legal notice to the said companies for misusing your name without any authority or consent or permission etc. You can instruct them to withdraw your name from their report mentioning your firm as internal auditors.
You can inform the registrar of companies in writing stating that you did not audit the said companies in the period shown to have been audited by your firm and disclaim the responsibility.
You can issue a public notice in a newspaper about this and disclaim the liability of auditing of the said companies.
A corporate fraud occurs when a company or an entity deliberately changes and conceals sensitive information which then apparently makes it look healthier. Companies adopt various modus-operandi to commit such corporate frauds, which may include miss-information in the prospectus, manipulation of accounting records, debt hiding etc. The aspect of falsification of financial information includes false accounting entries, false trades for inflation of profits, disclosure of price sensitive information which comes under the ambit of insider trading and showing false transactions which result in attracting more investors and lenders for funding.
Fraud in relation to affairs of a company or any corporate body as defined in S.447 of the Companies Act 2013, includes any act, omission, concealment of any fact or abuse of position committed by any person or any other person with the connivance in any manner, with intent to deceive, to gain undue advantage from, or to injure the interests of the company or its shareholders or its creditors or any other person, whether or not there is any wrongful gain or wrongful loss..
Any person who is found guilty of fraud shall be punishable with imprisonment for a term which shall not be less than six (06) months but which may extend to ten (10) years and shall also be liable to fine which shall not be less than the amount involved in the fraud, but which may extend to three (03) times the amount involved in the fraud. Where the fraud in question involves public interest, the term of imprisonment shall not be less than three (03) years.
Undr section 448; If in any return, report, certificate, financial statement, prospectus, statement or other document required by, or for the purposes of any of the provisions of this Act or the rules made thereunder, any person makes a statement —
which is false in any material particulars, knowing it to be false; or
which omits any material fact, knowing it to be material