The Morrison government has killed off a gas exploration permit within 50 kilometres of Sydney’s coastline after a community and environmental backlash that threatened the government’s prospects in half a dozen key seats.

Visiting beachside Terrigal in the marginal Central Coast seat of Robertson, Prime Minister Scott Morrison said the government would reject an application to roll over the Petroleum Exploration Permit 11, or PEP 11, a zone covering more than 8200 square kilometres from Newcastle to Wollongong.