Ms Josephs had taken a personal interest in the project and given its steering group renewed energy, he said.
After 11 years of discussions, it was hoped construction would start this year - until ‘partygate’.
WHAT DID KATE JOSEPHS DO WRONG?
Ms Josephs hosted a leaving party at the Cabinet Office on December 17, 2020 where she was working as director general of the Covid Taskforce.
Despite her repeated denials it came out last week. She has now taken annual leave while councillors decide her future.
Mr Slater said she had been booked in to visit Attercliffe again this month.
He added: “Partygate is putting her off her job. It’s an unwelcome distraction.
“We were confident 2022 was when Attercliffe Waterside would rise from the ground, especially with the team Kate Josephs put together and her personal attention.
“Partygate has got nothing to do with Sheffield.”
WHAT IS ATTERCLIFFE WATERSIDE AND WHY IS IT DELAYED?
Mr Slater also said 2022 was the year developer Citu had to start delivering ’or move out of the way’.
Attercliffe Waterside is a 22-acre brownfield site centred on the Sheffield and Tinsley Canal and Woodbourn Road.
First discussed in 2006, it was put up for sale in March 2019 by three landowners, the Duke of Norfolk, Sheffield City Council and the Canal & River Trust.
It attracted nine bids and a winner was set to be announced that summer, but it was delayed twice.
A year later Leeds-based Citu was revealed as ‘preferred bidder’.
WHAT IS DEVELOPER CITU SAYING?
Chief executive Chris Thompson said: “Attercliffe Waterside is a highly complex scheme involving multiple landowners. Progress has been made on the acquisition work with the various parties. Once this is finalised, a planning application will be submitted and the scheme will continue to move forward.”
Jeremy Robinson, of commercial estate agent Fowler Sandford, who represents the Duke of Norfolk, said: “With regard to Attercliffe Waterside we have no comment on the matter.”
Sheffield City Council was contacted for comment.
Last year, the government imposed a target of 53,000 new homes in Sheffield by 2039.