I have been working at client location since 14 month. Initially, I had joined through consultancy A and there was prime vendor and vendor. I bypassed my employer (A) and vendor (B) and joined another consultancy (my current employer) but client and prime vendor were same.
Now, I got full time offer from client and there is no restriction from prime vendor. But, I have signed non competence(which says I cant join client till one year of project termination) though I was the one who got the project for my employer.
I have to give decision asap. will there any legal issue that I might face through my employer? I am getting good offer with great benefits so dont want to loose this offer. Suggestions please.

Read the contract, are the restrictions on joining another prime vendor or final client?

Your consultancy signs contracts with you Prime Vendor, as far as it is concerned your employer is working with Prime vendor and your consultancy working with vendor. You can just let the consultancy know you are moving to a diff company. Why even let them know? If you join your main employer its not like the HR will give out your info.

Thanks maxpayne for ur response.
They might know from different sources. And I am talking about the agreement that I have signed with consultancy, called non competency which says I cant join to the current client during or for a period of 1 year after the end of agreement.