Offering a discount/payment for referrals

I have had a number of referrals from existing cients in the last few weeks. o date I have grown my business from Sales letters with follow up calls, a telemarketing campaign and a little networking.

This year I have joined a lunchtime BNI group and am going back to the sales letters and will have someone follow up with a call.

However, given my referrals from existing clients are growing, I was cnonsidering writting to all clients stating that if they referred me I would offer x amount per new client - do you think this is a good idea?

How else can I use my existing client base to help grow?

Thanks in advance for any advice