The Westpac Rescue Helicopter Service (WRHS) says scammers on the Mid North Coast have been calling homes and going door to door asking for donations.

General Manager Richard Jones said the WRHS was alerted to the scam after it received calls from locals in the Taree area who were targeted and recognised the operation was a scam.

"These are generous people who have contributed to local fundraising events," he said.

"They know the service does not door knock and they wondered why they were being approached in this way."

He said the alleged scammers did not wear uniforms, whereas legitimate volunteers would wear identification.

The service does not fundraise over the phone or door to door.

"We think it's invasive," Mr Jones said.

"We think that's an abhorrent way to fundraise so if someone knocks on your door please report it to the police."

The WRHS is funded by donations, NSW Health and the Ambulance Service of NSW, and has undertaken more than 30,000 missions since it began in 1975.