West Auckland Police have been left blushing after a concerned resident reported suspicious activity, only for police to realise it was their own officers doing a good deed.

On Thursday a Green Bay resident noticed a silver Commodore pull a U-turn and approach a woman walking alone on Godley Rd.

But when police investigated the matter, they realised it was, in fact, their own car that had made the U-turn to approach the woman.

Police took to Facebook following the gaffe, explaining they had approached the woman to offer "prevention advice".

"Last night, a rightly concerned member of the public phoned in having seen a silver Commodore do a U-turn and approach a female walking along Godley Road, Green Bay.

"Conveniently, one of our Crime Squad units was nearby and did some areas for the silver Commodore – until they realised they were in fact driving a silver Commodore and had earlier done a U-turn to provide some prevention advice to a lone female walking on Godley Road!

"Excellent catch by Crime Squad (of themselves!), and equally good work earlier to look after a potentially vulnerable female walking the dark streets."

West Auckland residents saw the funny side, with many praising police while also giving them some well-deserved banter.

"Imagine the face drop moment when they realised!" one person wrote.

Another said: "Some top quality investigative work there."

"Excellent ... so funny but great the person phoned it in!"