Assalamualaykum, Feroz khan. Here’s a concise overview and guidance regarding your situation with a third-party PERM filing while employed elsewhere on H-1B:

PERM Application Through an External Consultant
Legality and Feasibility:
The PERM labor certification must be filed by a U.S. employer—not by the employee or a consultant directly—on behalf of a specific foreign national for a specific job offer. If the consultant is acting as a representative for a genuine employer who is willing to sponsor you, this is permissible. However, if the consultant is not representing a legitimate employer with a bona fide job offer, the process may not be valid or could risk denial or future immigration issues.

Working Elsewhere During PERM Filing:
You can be employed by your current H-1B employer while another company files PERM for you, as long as the PERM process is for a future job offer and not your current position. There is no legal requirement that you must be employed by the PERM sponsor during the PERM stage, but the sponsor must intend to employ you once you receive your green card.

Impact on Current H-1B Status
H-1B Status:
Filing a PERM through a third-party employer will not affect your current H-1B status with your current employer, as long as you continue to meet the terms of your H-1B and do not violate any conditions (such as working for the PERM sponsor before you have the appropriate work authorization).

Employer Awareness:
Your current H-1B employer does not need to be informed about the PERM process initiated by another company. However, if your current employer is your H-1B sponsor, you may need to consider any contractual obligations or company policies regarding outside immigration filings.

Possible Complications:
If your current H-1B employer becomes aware and is not supportive, there could be workplace implications, but not legal immigration consequences unless you violate H-1B terms.

Recommendations
Ensure Legitimacy:
Verify that the consultant is working with a genuine U.S. employer willing to sponsor you for a real job. Avoid any arrangement that seems to be only for immigration benefits without a bona fide job offer.

Consult an Immigration Attorney:
Given the complexity and potential risks, consult a qualified immigration attorney before proceeding. They can review the specifics of the offer and help ensure compliance with all legal requirements.

Timeline and Coordination:
The PERM process is lengthy and can take several years, especially for nationals of backlogged countries like India or China. Coordinate carefully with both your current employer and the PERM sponsor to manage your immigration status throughout the process.

A greencard petition is for future employment and does not affect your current H1B status or employment. As long as the new sponsoring company is reputable, you can move forward.