Some of Auckland's most popular coastal spots are becoming rubbish dumps as floating piles of garbage wash up on them.

Boaties, strong winds and discarded household junk are being blamed for clogging once-pristine coves, islands and beaches this summer.

And swimmers at some favourite spots say they have been contending with an onslaught of unpleasant rubbish.

Strong easterly winds and heavy rain after a dry period have been blamed for the buildup of waste in the water and on the sands of North Shore beaches.

The finger has also been pointed at boaties disposing of waste in the Hauraki Gulf.

Residents and swimmers at North Shore beaches say bays have been contaminated this month by disgusting litter apparently thrown overboard.

Rangers at Long Bay Regional Park make daily clean-ups at 4am to keep the beach in a reasonable state.

Long Bay resident Kathryn Calvert said her family got out of the water last week after finding more than 20 tampons and used sanitary pads floating nearby.

"I've never seen anything like it. It's hard to believe someone would throw this in their back garden."

Complainants had been told by rangers that this year had been particularly bad for harbour pollution.

Love Your Coast, a volunteer clean-up last month, netted 200,000 pieces of rubbish from the shores of Rangitoto Island.

Waitemata Harbour Clean-Up Trust spokesman Hayden Smith said that after eight years of patrolling Auckland's waters, he was no longer surprised when unpleasant items were found in the gulf.

This year, a combination of summer crowds and weather conditions had resulted in a large amount of junk at North Shore swimming spots.

"We've had a considerable dry period, so when it rains, everything up on the streets gets washed immediately down through all the drains of the city.

"Another factor is that we've had so many easterly winds blowing straight onshore, blowing rubbish back on to Long Bay and other parts of the Shore."

Usual tidal currents push rubbish to the islands in the gulf - Rangitoto, Motutapu, Motuihe, Waiheke and Little Barrier.

The Waitemata Harbour Clean-Up Trust said 90 per cent of rubbish in the sea was blown by the wind or carried through stormwater drains.

Some prevention measures have been taken - nets have been placed at the end of some North Shore stormwater drains to prevent large objects getting into the sea.

But Mr Smith said much of the litter, especially large objects, had come from boaties in the Hauraki Gulf.

As well, anglers threw bait bags and packaging into the Waitemata.

But Recreational Fishing Council head Geoff Rowling said he believed fishermen were more likely than the average boatie to respect the sea.

"Those who are looking to the marine resources to provide them with food take the care of the marine environment very seriously."

Collected items such as toiletries suggested it was boaties, not fishermen, who were dumping their waste.

Since the trust was set up in 2002, its volunteers have pulled enough garbage - - from lolly wrappers to car tyres - out of the harbour to fill nearly 80 large shipping containers.

A day's clean-up by the trust gathers 3000 to 3500 litres of junk, a figure limited only by the number of volunteers on its single boat.

The most common item is plastic bottles, but larger items are found, including car tyres and even a kitchen sink.

Mr Smith said the amount of rubbish had remained consistent over the past eight years.

But the number of clean-up volunteers and the level of community concern for the harbour's health were increasing.

The Love Your Coast campaign gathered 4000 helpers, 2000 in Auckland.

Picking rubbish out of the harbour is labour intensive, so the trust says the best idea is to stop it being dumped.

As well, Mr Smith said, businesses and manufacturers needed to be aware of the environmental impact of their products and packaging.