An investigation into Christchurch City Council's decision not to ban sex workers from St Albans, is being welcomed by the local MP.

The question came up after complaints from residents, and the Council's refusal to enforce the Public Places Bylaw.

People living there have complained about condoms and needles littering the streets.

The bylaw makes it illegal to carry out a commercial activity in a defined places.

The MP for central Christchurch Duncan Webb said the Ombudsman will not look at the legality of the issue but rather whether the council's decision not to enforce the bylaw is reasonable.

"It says that it is not permitted to undertake commercial activity in a public place, and you know the activity of the sex workers that is clearly commercial and it's clearly in a public place."

Webb said Christchurch City Council should be required to use its powers to stop the activity, even though the task will be a difficult one.

"I make no bones about it, enforcing this bylaw in respect of street based sex workers will be difficult, it will be expensive and time consuming."