The Christchurch City Council have defended their handling of the contamination risk to the city's wells.

The council said it has not been idle after discovering the risk to the city's water supply last week.

The Canterbury Water Assessor removed the secure bore status on the 22nd December after possible groundwater contamination risks were revealed.

However, the public was only informed yesterday after a council meeting.

Council's CEO Dr Karleen Edwards said their priority over the Christmas break was getting a plan in place.

She defended the decision not to tell the public sooner.

"I guess the risk has been relatively small. The consequences are large but it's really in terms of being able to decide what the plan is, how we're going to approach that."

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The move has been met with support though, with Water New Zealand technical manager Noel Roberts saying it is a no brainer.

"Knowing that the well heads are not intact, I would certainly endorse putting chlorination in now and investigating further down the track whether that stays permanent or whether an unique type of treatment goes in or even both those options."

Roberts said it's not a popular choice to make.

Christchurch-based MP Gerry Brownlee seems to agree, telling Chris Lynch this morning that he doesn't believe in the concept of mass-dosing people with chlorination.

The MP for Ilam MP said residents deserve a decent look at the well reports before action's taken.

"If you recall just after the February 11th earthquake, the system was all back and running, and safe, in just four days. Now if it's about ingression into certain wells, we've got a right to know exactly what those reports say."

The city's drinking water is drawn from 156 wells, located at 56 sites across the city.