Members of the group Let Pompey Breathe met with other eco campaigners to host a ‘Clean Air Protest’.
They called on the city council to commit to finding and implementing solutions for poor air quality, which has been linked to serious health conditions.
Tim Sheerman-Chase, from Let Pompey Breathe, said: ‘This was the biggest public health issue we were facing before Covid, but it hasn’t gone away.
‘Air quality is linked to the shortened life expectancy of around 100 people in Portsmouth every year.
‘We’re trying to keep the pressure up to get the council to take it seriously.’
Environmental activists say that they doubt Portsmouth City Council’s proposal for a class B Clean Air Zone, which would aim to bring air pollution within safe limits by charging buses, coaches, taxis, private hire vehicles and heavy goods vehicles, would go far enough in addressing the problem.
Tim added: ‘The council has known we’ve had a problem since 2010.
‘The local authority has the responsibility to sort this out but haven’t been given the resources to sort it - there’s not much help from central government.’
Campaigners marched with signs from Kingston Crescent Surgery towards Guildhall Square to mark Clean Air Day.
Cathy Pitt, from Friends of the Earth, said: ‘I want cleaner air in Portsmouth, and I want the council to step up.
‘No wonder we’re having these problems when they’re building all these new houses and chopping down trees.’
Fellow protester Andy Ames, from the Hampshire and Isle of Wight Wildlife Trust, runs Wilder Portsmouth encouraging people to create and enhance wild spaces where they live.
Andy said: ‘My big driver is to put the green back in the city.
‘People talk about the heart of the city, but I want to make sure it’s got lungs.
Councillor George Fielding met the campaigners in Kingston Crescent at the beginning of their walk to show his support for the cause.
He said: ‘We’re standing on one of the most polluted roads in the city today.
‘It’s increasingly important that we take seriously the issue of poor air quality - the council needs to take it incredibly seriously.’