Conservative politicians have called for a Labour politician to "put up or shut up" after he made claims of "truly shocking, industrial-scale corruption" in Teesside.
Middlesbrough MP Andy McDonald, a former shadow cabinet member under both Sir Keir Starmer and Jeremy Corbyn, made the comments last month in the House of Commons about the redevelopment of the Teesworks site.
There have been calls from Labour for an investigation into the project - which Conservative mayor Ben Houchen has welcomed, saying there is nothing to hide.
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But Mr Houchen and local MPs Simon Clarke and Jacob Young have called for Mr McDonald to repeat his comments outside the House of Commons - where he is not protected by parliamentary privilege.
Parliamentary privilege can be used to break injunctions, and also means anything said cannot be subjected to claims of defamation.
The allegations centre on the Teesworks site, which was previously home to the Redcar steel facility.
It is currently being developed by the South Tees Development Company [STDC] - chaired by Mr Houchen - alongside private investment.
Mr McDonald claimed the "only growth being delivered" by the site was to "Ben Houchen's pals Messers Musgrave and Corney" - two people who are working on the project.
According to reports in the FT, Chris Musgrave and Martin Corney and their companies have control of 90% of the STDC.
Simon Clarke, the MP for Middlesbrough South and East Cleveland, tweeted: "Andy McDonald needs to put up or shut up - either repeat his corruption allegation outside Parliamentary privilege, or apologise for it and withdraw it."
Jacob Young, the Tory MP for Redcar and Cleveland, said: "Andy McDonald keeps hiding behind parliamentary privilege to smear our progress, and even slippery Starmer won't back him.
"We will keep focusing on creating long-term sustainable jobs on the former Steelworks.
"We won't let the wreckers win."
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Mr Houchen told the BBC that Mr McDonald was a "coward".
The government is currently considering whether or not to order a full National Audit Office (NAO) inquiry into the Teesworks project.
Shadow levelling up secretary Lisa Nandy wants an investigation to take place, and Mr Houchen has said he would welcome the probe as well.