A Sydney mum has slammed Prime Minister Scott Morrison contrasting his vacation with her 71-year-old volunteer firefighter father who hasn't gone on holiday for years because of his sense of duty.

In a social media post, Sydney resident Angela Higgins explained how her father had recently retired and was looking forward to a long overdue holiday. However, after a family member fell ill, he cancelled the trip.

"Mum and Dad put their plans on hold and became full time carers in their home," her open letter to the PM reads.

"(They) were just setting off on that delayed holiday when Dad's Mum took a fall. Once again they became full time carers … until they were able to find a place in a suitable care facility.

"With Grandma now well looked after, Mum and Dad could finally take some time out but then these fires started and they show no signs of stopping."

The septuagenarian has been battling fires all season with Ms Higgins posting a picture of her father kitted out in his bushfire wear.

"Mum took this photo at 9am when Dad returned after a full night of fighting the Hat Hill Rd fires in Blackheath," Ms Higgins said. "He's exhausted but still smiling."

"Mum manages everything at home and is well prepared so that Dad can go out to protect other people's homes. They are a team, a force to be reckoned with but they are tired.

"While my Mum and Dad won't get to take a holiday this year, they could really do with a break," she told the Prime Minister.

"And so I am asking you please, now that you have had some time out with your family, please return revitalised and refreshed and DO something more. More resources, more empathy, more appreciation and support."

The plea has been shared more than 1000 shares and has three times as many likes.

One Facebook user said: "That holiday is truely (sic) well deserved". Another called the couple "the quiet heroes" of Australia.

The viral post comes on the heels of Scott Morrison returning from his Hawaiian holiday. Mr Morrison has apologised for his US jaunt.