I have submitted a Starting Grant proposal in response to the ERC Starting Grant Call 2014 wit ha host institution in an EU-associated country. Can I submit a similar SNSF Starting Grant proposal with a Swiss host institution?

Yes. It is possible to submit a parallel grant to the ERC with a host institution in an EU or associated member state. However, the applicant must inform the SNSF of any parallel submissions, and only one grant can be obtained.