Over the next month, we're going to hear a lot from Andy Burnham – as he bids to return to Westminster – about his role in rooting out the Asian grooming gangs and getting justice for the countless children who were their victims.

He will claim he fought the police and social services to expose their failure to act. And he will imply that the scandal is largely over, thanks to his intervention.

If Burnham is elected as Makerfield's MP at next month's by-election, there's a strong chance he could soon be Prime Minister. And that concerns me.

I have no party allegiance. I left my role as a Detective Constable in Rochdale in 2012 in protest at the force's mishandling of two child sex abuse rings. Since then, I've campaigned for the victims of grooming gangs and exposed the failures of institutions – from the police to social services – in preventing group-based child sexual abuse.

I've criticised Tory inaction. I've attacked Labour letdowns. And I'm not afraid to pick a fight with politicians of any creed in my determination to keep a spotlight on police failures to address grooming gangs.

It doesn't matter to me what party Burnham represents. He should not be PM because he does not fulfil his promises. He happily takes the credit for other people's battles, but he lacks the steel to keep fighting when the stakes get high.

In my experience, he doesn't finish the job. Instead, he looks for the easy way out. Don't just take my word for it. Ask Victoria Agoglia's grandmother, Joan.

Victoria was 15 when she died from a drugs overdose. Two months earlier, she told Joan that men were injecting her with heroin and raping her. Joan tried desperately to make the authorities believe that her granddaughter, who lived in a council care home, was in life-threatening danger.

'I phoned them and I phoned them and I phoned them, but nobody cared,' she said.

Fourteen years later, Burnham, as Mayor of Greater Manchester, finally took action and ordered an investigation. This followed a BBC documentary, The Betrayed Girls, of which I was a central part, highlighting the extent of the grooming gangs crisis.

Burnham pledged to hold a second inquest to discover the true causes of Victoria's death. But seven years on, this still hasn't happened. Manchester social services have been allowed to maintain that it did everything possible to prevent Victoria's death when, in reality, many workers at the care home have admitted that they were aware of the abuse she was suffering. Her story is just one among thousands.

I've known Burnham for nearly ten years and I've pleaded with him many times to make good on his promises. But he simply melts away. I have been reluctantly driven to the conclusion that he is unwilling to make the tough decisions a real leader will.

He has charisma, with a gift for saying what people want to hear. I liked him when I met him and I'd rather go to the pub with him than with Sir Keir Starmer, who failed to tackle the grooming gangs while he was Director of Public Prosecutions.

But credit where it's due: Burnham struck two blows against the gangs, by instigating independent reviews in two police investigations, Operation Augusta in Manchester and Operation Span in Rochdale, which were both spineless.

Thanks to his intervention, my stance, held since 2013, that these operations were failures was vindicated. For that I am grateful.

But a third review, into widescale sexual abuse by Asian gangs against children in Oldham, amounted to little more than a cover-up. And the 'assurance review' that followed – so-called because it was meant to assure the public that the reign of the gangs was at an end, and that Greater Manchester Police were finally dealing with the victims properly – was not honest, transparent, or fit for purpose. It was so poor that I had to withdraw myself and my charity, the Maggie Oliver Foundation, from any association.

The two independent professionals who delivered the first three parts also resigned.

We made it clear to Burnham why we were taking such a step. He still pressed ahead without speaking to a single victim, meaning the conclusions were largely worthless.

As Mayor of Greater Manchester, Burnham is also Police and Crime Commissioner. It's his job to hold senior officers to account and confront the incompetence that allowed mass abuse to go largely unchallenged.

He had the opportunity and he wasted it. He promised he would do it and he didn't. There is an ongoing cost in lives lost and victims who suffer and, in my opinion, Burnham holds some responsibility for that.

This country needs a leader who isn't afraid to shine a light in dark corners. We need a leader with courage and integrity.

We need someone as good as their word. You'll hear a lot of words from Burnham but, based on my experience, whether he will honour them is another question entirely.

The Maggie Oliver Foundation helps survivors and those at risk of childhood sexual abuse and exploitation.