The short answer is YES.
The wireless router uses 2.4GHz (see the specs on the manufacturer’s website – http://www.netgear.com/Products/RoutersandGateways/SuperGWirelessRouters/WGT624.aspx?detail=Specifications) and so does your phone (from what you said).
As the previous answer says, your best choice is to get a different phone. DECT would be my choice, as this uses different frequencies, and is almost totally immune from interference, so they will co-exist happily. (and throw the old phone away !)