Nigel Farage has revoked the party membership of a Reform UK council leader accused of racially abusing Sadiq Khan, David Lammy and other public figures online.

Ian Cooper, the leader of Staffordshire county council, allegedly called the London mayor a “narcissistic Pakistani” and said migrants were “intent on colonising the UK, destroying all that has gone before”.

In a post this year attacking Lammy, the justice secretary, Cooper allegedly wrote: “No foreign national or first generation migrant should be allowed to sit in parliament.”

He also allegedly abused the British-born lawyer and women’s rights activist Dr Shola Mos-Shogbamimu, calling her “Dr Shaga Bing-Bong” and saying it was “time she F’d off back to Nigeria. She’d feel more at home there.”

After days of pressure, Reform UK said on Friday it had revoked Cooper’s party membership. He is also no longer the leader of Staffordshire county council, a local authority responsible for more than a million people.

A Reform UK spokesperson said: “Following an investigation into the failure to declare social media accounts during the candidate vetting process, Cllr Ian Cooper has had his membership of Reform UK revoked.”

Cooper, who has not responded to the allegations, was Reform’s parliamentary candidate for Tamworth in a byelection in 2023 and again in last year’s general election.

He was elected as leader of Staffordshire county council in May as Reform won swathes of local authority seats across England and he is listed as the interim chair of the party’s Tamworth branch.

Nine Labour MPs from across the region called for Cooper to resign over the posts, which were first revealed by the anti-fascist group Hope Not Hate and shared with the Guardian.

Cooper and Staffordshire county council have not responded to repeated requests for comment.

In posts shared with the Guardian this week, Cooper allegedly told the broadcaster Sangita Myska this year that she was English “only in your dreams”, adding: “You are neither ethnically, culturally or historically English. Your diaspora isn’t NW European. All you have is a piece of paper entitling you to British citizenship.”

In another post a year ago, he allegedly said it was “a lie” that diversity was Britain’s strength and claimed that migrants from the “global majority south” were “intent on colonising the UK, destroying all that has gone before”.

He is also alleged to have said diversity, equity and inclusion schemes were disguising “oppression” and enabling a situation “where indigenous people are actively removed or excluded and not allowed to complain”.

Two other Reform UK politicians were suspended last month over offensive messages. Laura Anne Jones, the sole Reform UK member of the Senedd, had used a racial slur in a discussion about the potential threat of China using TikTok for espionage.

In Lancashire, the councillor Tom Pickup was suspended for calling Keir Starmer a “dicktaker” in a post to a WhatsApp group where members allegedly called for “mass Islam genocide”.

Reform UK said Martin Murray, previously Staffordshire county council’s deputy leader, had been appointed interim leader until the group elected a new permanent leader.

A spokesperson for Staffordshire county council said: “Reform UK has confirmed this evening that they have revoked the party membership of Ian Cooper, the leader of Staffordshire county council.

“Reform UK has announced that Martin Murray will be the interim leader of the council’s Reform UK group. Any proposals to nominate a new leader of the council will need to be agreed at a meeting of full council. We will work with the administration on the next steps.

“Our job will be to continue serving the residents of Staffordshire and delivering services without disruption.”