Councillor Gerald Vernon-Jackson insisted the scheme would only be a temporary measure and was hopeful that come the beginning of 2023, it may not be needed at all.
The zone comes into force on Monday and is part of a major drive to cut down unhealthy emissions and improve the city’s woeful air quality.
Private cars, vans and motorbikes will not be charged to drive in the zone.
However, the ‘oldest, most polluting’ buses, coaches, lorries, taxis and private hire vehicles will need to pay between £10 and £50 a day.
But Cllr Vernon-Jackson said this measure could be over in little more than a year.
He said: ‘My understanding is that because people have changed cars and updated to newer and better ones that we’re likely to not have the levels that are wrong in two years time.
‘I hope within a year or year-and-bit, the clean air zone could be removed. If we can get down to a sustainable level there will be no reason for the clean air zone to remain.’
Portsmouth is the most densely populated city outside London, with individual vehicles contributing to 50 per cent of air pollution on the island.
Portsmouth City Council was identified by the government as one of more than 60 authorities that had excessively high air pollution levels.
Cllr Vernon-Jackson said the authority was not keen on the introduction of a clean air zone and feared it could have a knock-on effect on business.
The Liberal Democrat leader added he felt there were other, ‘more effective’ ways of cutting pollution.
‘Everybody realises there are much better ways of improving air pollution in the city in a much more sustainable way but the government is just not interested in that,’ said Cllr Vernon-Jackson.
‘They’re not interested in doing a scrappage scheme to get the most polluting vehicles off the road or to give people decent bus passes so they can leave the car at home and use the bus.
‘I’m disappointed we’re having to do this because there are much better and more effective ways. The government is profoundly uninterested in anything else.’
Previously, health bosses have warned that breathing in the city's polluted air was the equivalent to smoking 142 cigarettes a year.
The British Heart Foundation claimed that Portsmouth residents were at risk of an early death and said air pollution must be declared a ‘public health emergency’.