Reform UK has said it will no longer co-operate with a BBC documentary about the party following a row over how a speech by US President Donald Trump was edited.

The BBC had commissioned an outside production company, October Films, to make the programme, which was due to air in January.

The company was involved in the Panorama documentary about Trump which has triggered a major row at the broadcaster, though was not responsible for the editing of the speech, which was done by BBC staff.

An internal Reform email seen by BBC News said the production firm had “conducted themselves professionally” on the project but advised members to decline to participate with filming going forward.

October Films has been approached for comment, while the BBC said it does not comment on in-development projects.

The documentary was due to be called The Rise of Reform, and was to be presented by the BBC’s Laura Kuenssberg.

Its makers had been given “unprecedented access” to senior figures in the party, the internal Reform email said.

It is unclear whether the documentary will proceed without the party’s co-operation.

The email referred to the Panorama edit of Trump’s speech from 6 January 2021 as “disinformation”, and said a decision had been made to “cease engagement” with the documentary as a result.

It continued: “We want to be clear that October Films have always conducted themselves professionally, and there is no suggestion from our side that they would maliciously misrepresent Reform UK.

“However, following the Panorama documentary the trust has been lost, and both BBC and the production company will have to do a lot of hard work to regain that trust.”

The email advised party members to “politely decline to participate” if approached by the documentary team, and to withdraw consent for footage already filmed to be used.

One of the documentary’s subjects, Kent County Council leader Linden Kemkaran, said in a social post that she had “rescinded all permission” for footage gathered over several weeks to be aired.

The BBC has come under intense scrutiny over a Panorama documentary, titled Trump: A Second Chance?, which aired shortly before the 2024 US presidential election.

An edit included in the documentary spliced together parts of a speech made by Trump on 6 January 2021 in a way that made it look like he was explicitly urging people to attack the US Capitol.

In his speech in Washington DC, Trump said: “We’re going to walk down to the Capitol, and we’re going to cheer on our brave senators and congressmen and women.”

However, in the Panorama edit he was shown saying: “We’re going to walk down to the Capitol… and I’ll be there with you. And we fight. We fight like hell.”

The two sections of the speech were delivered nearly an hour apart – with the “fight like hell” comment taken from a section where Trump discussed how “corrupt” US elections were.

In total, he used the words “fight” or “fighting” 20 times.

The documentary aired last year but came to prominence this month when a leaked internal BBC memo which raised concerns about the edit was published by the Telegraph newspaper.

The memo was written by Michael Prescott, an external editorial advisor to the BBC’s editorial standards committee. It said Panorama had produced a “distortion of the day’s events” which would leave viewers asking: “Why should the BBC be trusted, and where will this all end?”

The fallout to the memo’s emergence has led to BBC director general Tim Davie and head of news Deborah Turness resigning from their positions.

Trump has threatened to sue the BBC for $1bn (£760m) unless he receives a full retraction, apology and compensation.

On Monday, BBC chair Samir Shah apologised for an “error of judgement” over the documentary.