York’s climate change chief cannot be sure that York Central will be a net zero carbon development, but said she believes it will be over time due to changes in technology.

Coun Paula Widdowson explained that while the 200 planned council homes will be carbon zero once built, the authority only owns five per cent of York Central land and so cannot dictate targets to others.

The 45 hectare site, owned primarily by Homes England and Network Rail, is expected to provide up to 2,500 new homes and more than one million square feet of office, retail and leisure space.

In April, Coun Widdowson was accused of “avoiding scrutiny” after failing to attend meetings to back up claims about York Central’s net zero credentials.

She told the council’s economy and place scrutiny committee: “York Central is the largest and most progressive regeneration site in the UK and it needs to be able to achieve net zero.

“That’s improving the fabric, improving the energy efficiency and lowering the transport miles.

“I know what the part that we are responsible for will do, which is the Passivhaus [building performance standard]. I cannot categorically state what the rest will be.”

All non-residential parts of York Central will hit the BREEAM excellent rating, meaning they will be in the top ten percent of new non-domestic buildings for energy performance in the country.

The site will be supplied with electricity but no gas, and the possibility of a district heating network is being explored.

Director of economy, regeneration and housing Tracey Carter said net zero was a “work in progress” but that the mood music from within the York Central Partnership, which is delivering the scheme, was “very positive”.

Ms Carter said Homes England, Network Rail and the National Railway Museum all had their own carbon targets, but reminded councillors of the limitations of land ownership.

“The rest of it is down to nudge, influence and collaboration,” she added.

“We can’t stand up here and say to you this is going to be carbon zero, because that’s not within our control and our destiny, but we are doing our utmost to ensure that it’s as good as it can be.”

A development partner for the vast majority of York Central is currently being sought and should be in place by May 2023.

Labour’s deputy leader Coun Pete Kilbane said after the meeting that Coun Widdowson’s “lofty claim” that York Central would be net zero was “not worth the paper it is written on”.