Kevin Sinfield has criticised the government's failure to deliver on a £50 million pledge to fund research into motor neurone disease (MND).
The rugby league legend, who has won widespread plaudits for raising millions of pounds for MND charities through a series of endurance challenges, said there was "no valid reason" why ministers had yet to provide money promised by former Prime Minister Boris Johnson a year ago.
The ex-Leeds Rhinos player said: "MND is not incurable, it's just underfunded. There are people dying - families are being ravaged and that just isn't right.
"I can't see any valid reason, there isn't a reason, why that money is being held back. Not a penny has crossed over. That's the bit that disappoints me."
Mr Johnson committed £50million to funding research in November last year – a move which he said would "transform the fight" against MND.
But there has been criticism of the delays in providing the money, including from the family of Rob Burrow. Sinfield's former teammate was diagnosed with the disease in 2019 but has continued to campaign to raise awareness about the condition.
Sinfield questioned the government's commitment to its promise during a press conference on Thursday – days after he completed his third fundraising challenge, which saw him run seven ultra-marathons in seven days across Scotland and the north of England.
He has raised more than £7million in total, most of which has been donated to the MND Association and the appeal to build a MND research centre in Leeds in Burrow's name.
He added: "I do understand with anything like this there’s an element of red tape and bureaucracy that needs to happen.
"But then I look at some of the other ways the government has spent money over the last couple of years and I don't think it has been scrutinised in the way this is being scrutinised."
A spokesperson for the Department of Health said the government had invested millions of pounds in MND research.
They added: "We remain committed to spending at least another £50million to help find a cure to this awful illness.
"We’ve already funded clinical trials for various drugs which have shown promise in tackling MND, and we encourage researchers to make applications for this funding – which is available right now."
Speaking at the press conference, Sinfield also hinted that his third charity challenge may not be his last.
He said: "I did say that all good books and films are in threes, and we did call this the trilogy.
"When I addressed the group before we set off I did say that this would probably be the last run, but I did caveat that by saying Rocky 4 was my favourite Rocky, so we'll see."
Although his next challenge might not be a run, next year a marathon in Rob Burrow's name will take place in Leeds and Sinfield said he would be there.
He added: "All being well Rob will be on that start line and I'll push him round."
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