Steve Barclay asked if incinerator plans could be blocked

Environment Secretary Steve Barclay personally intervened to ask for advice on whether ministers could stop incinerators being licensed across England, including a controversial project in his constituency, the BBC understands.

Mr Barclay made an urgent request to government lawyers the day after planning permission was granted to build the waste plant at Wisbech in Cambridgeshire.

It is understood that MVV Environment, the company behind the plant at Wisbech, has now threatened the government with legal action after a temporary ban on permits was put in place.

Officials have previously raised concerns about Mr Barclay's involvement.

Mr Barclay has said that he had "previously flagged" his constituency interest and "said the policy needed to be delegated to another minister".

Under the Ministerial Code, ministers are expected to ensure there is no conflict of interest with their job as a constituency MP.

• Fresh questions for Barclay on incinerator decision

• Incinerator opposed by Barclay sees permit delayed

• Barclay apology over role in local waste project

The decision to pause issuing new operating permits across England was made in April by a junior minister, Sir Mark Spencer, after Mr Barclay recused himself from decisions on incinerators.

Mr Barclay has said that he formally stepped away on 27 February.

The BBC has now seen a request for advice, understood to have to been to sent to lawyers by an official in Mr Barclay's ministerial office, almost a week earlier on 21 February.

It said that "the secretary of state has asked whether a secretary of state/minister can stop new permits and/or revoke ones for sites not in use until an assessment has been made of the need for residual treatment?"

A new incinerator needs both planning permission and a permit to go ahead.

Just under a week later, a junior minister, Robbie Moore, wrote to the Environment Agency saying he intended to halt decisions on permits for up to a year.

In legal advice, which was leaked to the BBC, a top government lawyer warned the plan would be "unlawful" and raised "serious concerns of perceived bias".

Sir James Eadie KC also warned that if a legal challenge came to court, ministers and advisers would have to turn over WhatsApps and details of conversations relating to the policy.

Sources close to Mr Barclay have insisted he had made it clear to officials from the start that incinerator policy would have to be dealt with by another minister.

The BBC understands that lawyers working on behalf of MVV Environment have written to the Department for the Environment, Food and Rural Affairs threatening to take legal action if the pause on permits is not lifted.

Both MVV Environment and the environment department have declined to comment on possible legal action.

The government has said the pause on deciding permits was to allow environment department officials "to lead a piece of work considering the role of waste incineration in the management of residual wastes in England".

It is set to last until 24 May but could be lifted earlier.

Anti-incineration campaigners have said such an assessment is long overdue, as Wales and Scotland already have moratoriums in place which stop incinerators being built.

Industry insiders have suggested that an imminent pause on permits in England had not been expected