The UK’s longest serving mayor could see his post wiped out if he’s defeated in a fierce new Labour selection battle, his challenger has warned.

Rokhsana Fiaz promised a referendum on the directly-elected mayoral system in London’s Newham Council as she claimed incumbent Sir Robin Wales ran a “one-party state” that lacked accountability to the public.

In an interview with HuffPost UK, Fiaz also accused Wales of “dog whistle” tactics after he blamed “community politics” for irregular sign-ups of Labour members determined to unseat him.

But Wales hit back at critics of his 23-year leadership in the East London borough, and warned that Tower Hamlets showed what happened when some minority ethnic party activists separated residents rather than brought them together.

The Mayor – who battled Militant in his youth – also told HuffPost that if he was reselected he would urge Labour to get his successor for the mayoralty in place within two years.

Wales is seeking an unprecedented fifth term in office in this May’s election, but faces an eleventh-hour party battle after local members decided he should not be automatically selected as their candidate.

Wales and Fiaz were shortlisted by Labour HQ on Wednesday, and are the only two contenders. The open selection race will be determined by a one-member, one-vote ballot running from March 1 to March 16.

The contest is being watched closely by all wings of the party nationally, not least following the resignation of Haringey Council leader Claire Kober.

Fiaz told HuffPost that Newham, where Labour has 59 out of the borough’s 60 councillors, lacked transparency and was run by a “very top down, hierarchical leadership style”.

She pledged to hold a referendum on the directly-elected mayor model in her third year, after a probe by a new democracy commission.

If the public decides to go back to a traditional council leader and cabinet, Newham would be only the third such area in the country to do so since Tony Blair set up the new system in the 2000s.

Fiaz accused Wales of an “innate insecurity” with a sense of “entitlement” and claimed he had “squandered” £52m in public money on the former Olympic stadium that is now home to West Ham football club.

She said she wanted to become the country’s first directly elected female mayor from a minority ethnic background and hit out at Wales’ remarks suggesting Muslim party members had been signed up in big numbers to vote against him.

Wales has suggested up to 200 new members cast votes against him in a trigger ballot and referred to ‘community politics’ being brought into play.

“I think [the phrase] ‘community politics’ is a really lazy attempt by some individuals to play pretty appalling dog-whistle politics. It’s disgusting,” Fiaz said.

But in a separate HuffPost interview, Wales pointed to neighbouring Tower Hamlets, where the mayoralty was plunged into chaos and the party split by former Labour member Lutfur Rahman.

“Go to Tower Hamlets. See what happened in Tower Hamlets, we’ve got to oppose it, we’ve got to say we are together as one…if you look at Tower Hamlets, people want to separate people. [In Newham] 90% of people get on together here.

“Look at Tower Hamlets, people will get a group of people and bring them in. My policy is we will not fund single ethnic or single religious groups unless they are doing something for everybody.”

Wales also said he would “plead guilty” if the charge was making Labour so popular in Newham that it won nearly every council seat. 

He made a staunch defence of his record, saying he ran one of the most “radical, socialist” councils in the UK that delivered on Jeremy Corbyn’s plans for more homes, jobs and better public services.

Investment in the London Stadium was set to generate up to £160m in new homes and other regeneration, he added.

Hitting back at critics of his long tenure, he pointed to former Manchester United manager Sir Alex Ferguson, who quit after 27 years in the job.

“Alex Ferguson left and then we went ‘oh, this is a bad thing’. The question isn’t how long I’ve been here, the question is what I’ve done and what I plan to do,” he said.