"We want to be constructive," regional council boss Valérie Pécresse told a press conference to present her alternatives to the city council's controversial closure of part of the road along the right bank of the Seine to traffic.
The deputy mayor responsible for the scheme, Christophe Najdovski, was not impressed.
"If she wanted to have dialogue she could have talked to us rather than to the press," he commented.
Citing a survey commissioned by her regional authority that contradicted the positive findings of an earlier one done for the city council, Pécresse has proposed three choices, all of which would involve putting cars back on the river bank.
Cars would return Seineside
Two would reopen one lane on the lower riverside to cars, and have cars, bikes and buses on a higher level, which is currently open to traffic.
The third would have two lanes open to traffic on both the lower and the higher level.
In all cases there would be a speed limit of either 30km/hr or 50km/hr.
The aim is to have "less traffic, fewer traffic jams and more room for pedestrians, bicycles and public transport", according to the proposals' authors.
None are acceptable to the city council, according to Najdovski, a member of the Green party EELV.
"They mean blood and tears," he told Le Parisien newspaper.
War of statistics
The regional council's survey notes a negative impact on traffic in the city centre and an increase in noise pollution, "especially at night".
It also says that pollution rises when cars slow down because of heavy traffic.
Pollution watchdog Airparif responded by saying that it was too early to reach any serious conclusions.
"These figures are based on a theoretical and very localised calculation," it commented, adding that a reliable view of the effects on air in the Paris conurbation will only be possible after six months.
Earlier in the week Paris Mayor Anne Hidalgo presented an Airparif report that showed that pedestrians on the lower level breathe in 25 percent less nitrous oxide than those on the higher level, who in turn breathe in 10 percent less than pedestrians on the opposite side of the road.
Airparif warned that it had found "no clear trend that could be put down to the closure of the river banks alone" and said a further survey will be taken in the spring.
Najdovski insisted that "the reduction in traffic noted since October is confirmed" and that, while journeys are now longer than before the measure was introduced, they have not been lengthened by as much as predicted.
Right-wing to end free transport on high-pollution days
As from this month, motorists in Paris are obliged to have a sticker showing how much pollution their vehicle causes on their windscreens.
The dirtiest will be banned from the streets when pollution soars, as it did in December.
Then traffic was restricted according to licence plate numbers and public transport was free.
Pécresse has proposed abolishing free public transport on high-pollution days.
Air pollution causes an estimated 48,000 deaths a year in France.
NKM v Hidalgo
Another right-winger, Nathalie Kosciusko-Morizet, weighed in on Friday, accusing Hidalgo, who beat her in her bid to become the capital's mayor, of having "no consistent convictions" on the environment.
"Today Paris is a city stressed out by Anne Hidalgo's policies," she told Le Parisien.
The city council is now "an employment exchange for the Socialist Party", which faces probable defeat in this year's presidential and legislative elections, Kosciusko-Morizet said, accusing Hidalgo of counting on that defeat for the sake of her long-term political ambitions.