A Bangladeshi TV channel breached Ofcom rules by broadcasting a “one-sided” speech from Ken Livingstone during its Baishakhi Mela coverage.

Channel S was investigated after a viewer complaint likened a segment showing the Labour mayoral candidate to an “election rally”.

During the May 8 festival coverage in Tower Hamlets, Mr Livingstone criticised his Tory rival Boris Johnson and said he will improve housing, jobs and transport if he is elected London mayor next year.

After jumping on one of the main stages during the music and dance festival, he promised work “for the communities that Boris Johnson has neglected”.

Ofcom’s report, published today, said the rules required that “alternative viewpoints to that expressed by Ken Livingstone needed to be reflected”.

The report added: “This programme when considered alone gave a completely one-sided view on this matter of political controversy.”

Ofcom said it had to balance the audience’s and broadcaster’s right to freedom of expression with the impartiality rule.

Under the guidelines, broadcasters must show “due impartiality on matters of political or industrial controversy”.

The report went on: “While any Ofcom licensee should have the freedom to discuss any controversial subject or include particular points of view in its programming, in doing so broadcasters must always comply with the code.”

In its response to Ofcom, Channel S said the Mela was organised by Tower Hamlets Council and that representatives from different political parties had been invited but did not show up.

It said it did not feel it was in breach of the rule.