A Labour councillor has grilled the Tees Valley Combined Authority boss about the organisation’s plan B if pyridine is linked to the mass crustacean die-off.

A report by an independent panel convened by Defra chief scientific advisor Prof Gideon Henderson and the government’s top scientific advisor, Sir Patrick Vallance is expected next week. Cllr Steve Nelson, who sits on Stockton Council, asked TVCA chief executive Julie Gilhespie what would happen if the scientists found pyridine caused the mass die-off of thousands of crustaceans on the Teesside coast in 2021.

Defra has previously ruled that an algal bloom is to blame but campaigners disagree. Newcastle University academic Dr Gary Caldwell believes chemical pyridine is responsible and suggested the deaths were caused after sediment slippage led to an increase in maintenance dredging that disturbed historical toxins. PD Ports boss Jerry Hopkinson has previously said he does not think the maintenance dredging was to blame.

At the TVCA overview and scrutiny committee meeting on Thursday, Ms Gilhespie initially responded to Cllr Nelson’s question about a plan B by saying she wasn’t sure what he meant which brought an outburst of laughter from campaigners in the room. Cllr Nelson then responded: “What would happen if the report comes out next week and directly links the crustacean deaths to pyridine….I am just wondering what happens next in that eventuality. It’s quite possible the expert panel links the deaths.”

In response, Ms Gilhespie said: “We do what we have done all along, we follow government guidance. If the government guidance says we shouldn’t be doing it, we won’t do it…There are alternative ways we could approach it.

“But they are time-consuming and probably expensive and probably will mean that we won’t meet our contractual obligations. But at the end of the day, if that’s what the government tells us to do, that’s absolutely what we will do.”

Labour’s Cllr David Branson, who sits on Middlesbrough Council, wanted to know whether the TVCA thought there was an issue with pyridine. Ms Gilhespie responded: “We are not scientists, Defra is leading on this issue in terms of what the cause of the die-offs, which happened nine months before we started any dredging in the Tees.

“We follow what we are required to do under the MMO licence, the MMO guidance and under any guidance from Defra and we will continue to do that.”

The British Ports Association – which represents more than 100 port members covering 400 ports – has come out in support of Defra’s conclusions of an algal bloom. The BPA director of policy and external affairs Mark Simmonds said: “We have become increasingly alarmed at some of the statements and recommendations that have been made based on what we believe is unconvincing or erroneous evidence.”

The capital dredging for Teesworks is being carried out across three sites in the River Tees to allow for the construction of the £107m South Bank Quay. The first phase of dredging, which was deposited on land, started on September 1, 2022, and was completed on November 9. The second phase, which is being disposed of at sea, will commence before the end of March.

The maintenance dredging carried out by PD Ports, which goes on all year round, already works to maintain various depths along the river. The Teesworks dredging will ensure a 10.4m depth at the turning circle and in part of the river channel, while at the berth area, it will go down to 15.6m.

Conservationist Sally Bunce interrupted the meeting complaining that the questions read out were not the ones she submitted. The TVCA’s legal advisor said they were the ones that had been received. After the meeting, Ms Bunce said she thought it was “pretty shocking” that when she tried to clarify the questions she was told she couldn’t speak.

Cllr Steve Harker, a Labour member on Darlington Council, said he didn’t get any sense of curiosity from the TVCA to investigate further whether something had happened in the River Tees that it could be linked to.

Ms Gilhespie responded: “I think that is a misrepresentation. The amount of officer hours that have been spent on this issue over the last number of months is enormous.

“We are in regular contact with Defra, we trust the science, we trust the work Defra have been doing and that the independent panel will report, hopefully within the next few days, that will help us take that science further on. We have seen nothing to suggest to us there is a reason to not continue what we are doing.”

South Tees Development Corporation engineering and programme director John McNichols said there had been a robust process to secure permissions for the site. He added that it took 13 months to obtain the marine licence and 19 months from the inception of the project to the start of construction.

The dredging issue was also brought up by MPs in the House of Commons on Thursday. Shadow environment minister Alex Sobel said: “I just want the minister to confirm the independent panel has now been set up and, just because he was very quick in his answer, that they would be reporting this month. Because the fishing industry in the Tees is dying off, they need that report and they need that certainty to continue.”

Environment minister Mark Spencer replied: “The report will be given to the Secretary of State. I expect that report to come this month, as in January. We want to get those facts as soon as possible. We want to respond to the facts as they are presented.”