Buses could be upgraded to improve emissions following announcement of Sheffield city centre congestion chargeÂ

Ben Gilligan, director of public transport at South Yorkshire Passenger Transport Executive, said he wanted to work with bus operators to minimise any potential fare rises.

Sheffield Council said the '˜Clean Air Zone' will help tackle pollution and '˜save lives'.

The plans will be considered by the council's cabinet on November 27 and residents, businesses, taxi drivers and bus companies are set to be consulted from early 2019, with a possible implementation date of 2021.

Mr Gilligan said: 'We are really proud to have amongst the lowest fares in the country and we don't want to do anything that risks this achievement. There are many issues that affect ticket prices and we can't be sure what they will be in 2021.

'We want to work with bus operators to upgrade our buses to minimise any charges. As a bus partnership, we are clear our intention is not to increase fares to cover the cost of any pollution charges.'

Kevin Belfield, managing director of First South Yorkshire, said the company was working with the council on the proposals.

He said: 'Air pollution is a big challenge in all large cities. Bus operators play a vital role in helping to find solutions to reduce air pollution and we want to do even more. Buses also help to reduce emissions made by cars, as one double decker can take 75 cars off the road.

'We are working closely with Sheffield Council on this issue, and we're awaiting further details on the formal consultation for this new proposal.

'Figures show that buses contribute to 10 per cent of emissions. Over the last few years, the Council, First Bus and Stagecoach have invested millions in new ultra-low emission vehicles, including £9m this year.

'We have recently begun an extended program of upgrading older vehicles to help reduce emissions in the city to bring them up to the cleanest standards

'We are pleased that the Council will be seeking extra investment in the city's bus fleet from the government. Our ambition is to have really clean and compliant buses in Sheffield, which would mean that buses don't end up paying any proposed charge.'

The Sheffield Bus Partnership is a voluntary agreement between SYPTE, Sheffield City Council and bus operators First South Yorkshire, Stagecoach Sheffield, TM Travel and Sheffield Community Transport.

Coun Jack Scott, cabinet member for transport and development, said he hoped the charge will push people to choose more environmentally friendly vehicles.

He said: 'Air pollution is a major health problem and we know that people across the country including our children are breathing air that is not safe.

'The government is not taking this issue seriously at all. They have completely failed to give local councils the tools and resources we need, whilst forcing us to take the difficult decisions that are now needed because of their inaction.