Your employer may be breaking the law. There are special rules for employees based overseas coming to the UK for a short while, but 4.5 years is not a short period.
See the HMRC website at
http://www.hmrc.gov.uk/nic/work/emps-abroad.htm
Exceptions for employees sent from countries outside the EEA and without a Reciprocal Agreement or Double Contributions Convention
If an employee is sent by their normal employer from one of these countries to work in your business, and if all of the following conditions apply, then no NICs are due for the first 52 weeks after the employee arrives in the UK:
the employee is not ordinarily resident or working in the UK
they have been sent to work here temporarily by an overseas employer
the overseas employer has a place of business outside the UK (it doesn't matter if they also have a place of business in the UK)
the worker continues to be employed by the overseas employer
Once the period of 52 weeks finishes, you should begin deducting NICs from these employees in the normal way.
This may not apply to you so you could get advice from HMRC and perhaps Citizens advice. National Insurance also goes towards a pension and contribution based jobseekers allowance.
Your employer signed the WP1 application form agreeing that you would be employed on a class 1 national insurance basis, part of the work permit arrangements.
As far as getting ILR goes, you do need something from your employer to say you are still needed, and if UKBA asks for any more evidence, you are stuffed. How would you show that you are working in the UK? I have seen P60s with no tax paid for people from India, just in case your employer says that you do not get one if you pay no tax.
Maybe you should think about getting another employer (quickly though! before PBS), if the employer gets a visit, your permit could be revoked.
PP
