Steve Barclay under scrutiny for failing to declare potential conflict of interest | Steve Barclay

The UK environment secretary, Steve Barclay, has come under scrutiny for failing to declare a potential conflict of interest over a proposed waste incineration plant in his constituency.

Barclay has been a vocal opponent of the waste-to-energy plant in Wisbech, which is due to be one of Europe’s biggest such incinerators.

The most recent register of ministers’ interests shows Barclay has not declared the plant project in Cambridgeshire as a potential conflict of interest, even though it must be approved by the Environment Agency, which he oversees.

The BBC reported on Thursday night that officials at the Department for Environment, Food and Rural Affairs had raised concerns over the potential conflict of interest, even raising it with the ethics team at the Cabinet Office.

The department now says Barclay has recused himself over the approval decision, but Labour has raised questions over whether he has communicated with officials at the Environment Agency about it.

Steve Reed, the shadow environment secretary, said on Friday: “It is shocking that the secretary of state may have abused his position as environment secretary to prop up his constituency vote. The public rightly expect ministers to serve the British people, and not themselves. The environment secretary needs to immediately address these concerns.”

A spokesperson for the environment department said: “The secretary of state is recused from the decision. No decision has been taken. Mark Spencer is the minister responsible and would take any decision on this issue.”

The German energy company MVV Environment is planning to build the incinerator as a way to turn non-recyclable waste into energy. The plant would be able to burn more than 600,000 tonnes of waste a year and generate up to 50MW of power.

Barclay has long been an opponent of the plan, calling it “terrible news for our area”. Despite his opposition, his cabinet colleague Claire Coutinho approved the scheme last month in her role as energy secretary. But it must also get the go-ahead from the Environment Agency.

Following Coutinho’s decision, Barclay said: “As both a member of parliament and a resident living just outside Wisbech I remain strongly opposed to this proposal and will continue to do everything possible to fight it.”

The BBC reported that officials at the environment department had written to the government’s propriety and ethics unit over the issue, and that officials from that unit had discussed the matter with Barclay.

Reed wrote to Barclay on Friday morning asking for details of any communication between the environment secretary and his officials about the scheme, as well as demanding to know when he had recused himself from the overall decision.

No 10 on Friday refused to say when Barclay had recused himself. A spokesperson for the prime minister said: “It’s not uncommon that ministers to balance their work as a constituency MP with their roles of ministers and there are established processes which support that.”

They added: “We never provide a running commentary on those processes.”