Tens of thousands took to the streets of Dublin on Saturday in the latest mass protest against new water charges which have sparked widespread public anger.

The first bills for water from the new Irish Water utility are due next month after the government introduced the charges as a condition of its international financial bailout.

Saturday's demonstration is the latest protest after similar rallies late last year that forced Prime Minister Enda Kenny's coalition government into an embarrassing climbdown, slashing the charges.

Irish police could not provide an estimate on numbers but organisers put the crowd at 80,000. State broadcaster RTE cited observers as saying between 30,000 and 40,000 attended.

Dublin capped water charges at 160 euros ($172) for single households and 260 euros for others, and abandoned plans for pay-as-you-use meters.

But the Right2Water campaign, an umbrella organisation of dozens of local opposition groups, which organised Saturday's protest, said the issue was not going away.

"We have one objective and that's to seek a repudiation of the domestic water charges legislation," organiser Brendan Ogle said.

"We're going to ensure this is the major political issue in the next general election," he told AFP.

The government has insisted that the pricing changes they introduced last year provided "certainty, clarity and affordability" for charges.

Irish Water says about two thirds of those who are liable to pay the new charges have now registered with the utility, which represents 990,000 customers out of an estimated customer base of 1.5 million.

Under the old system, water was paid for through general taxation and services were operated by local authorities.

Many of the crowd carried the flag of anti-austerity opposition party Sinn Fein.

The crowd jeered and yelled "traitors", and chanted "Enda Kenny, not a penny" and "no way, we won't pay."

- 'To pay or not to pay' -

Roy Murphy from Clondalkin in Dublin was carrying a "we reject water charges" poster.

"This is going to kill the government at the next general election. How exactly do they think they've made it affordable?" he told AFP.

Another protester, Deirdre from Dublin, who asked not to use her surname, said the issue had become bigger than just water taxes.

"We're already paying water taxes through general taxation. But it's not just this, it's the pension cuts, the property tax," she said.

"I'm lucky enough to still be working but there hasn't been any salary increases in six years, but yet there's been lots of new taxes," she said.

Addressing the crowds, Socialist Party lawmaker Ruth Coppinger called for a mass campaign of non-payment when the first bills arrive.

"In 10 days' time every family in this country will receive a bill. To pay or not to pay, that will be the question," she said.

"The only way we can secure the abolition of water charges is by building mass non-payment."

Ireland must hold a general election by next April, and the government parties of Fine Gael and Labour are hoping economic recovery will boost their popularity.

Last week official data showed Ireland was Europe's fastest growing economy in 2014 and the European Commission forecasts a similar achievement this year.

Recent opinion polls show a resurgence in support for both government parties.

However left-wing lawmaker Joan Collins, who was taking part in Saturday's protest, insisted people were seeking an alternative.

"They are absolutely disgusted with this government which is carrying on the austerity measures," she told AFP.

"The polls go up and down but the main date will be the election and that'll be the decider."