The former Leeds rugby league captain and Bradford footballer joined a delegation of people calling for a £50million injection of funds over the next five years.
The group delivered a letter explaining that a cure for the disease is close to being found, provided there is a united approach to action and investment.
Darby, who announced that he had been diagnosed with the disease in September 2018, said: "After all of the hard work that has gone into the campaign it felt massively important to be here representing every family that has gone through MND.
"It'd mean everything to me to get the investment needed. UK researchers are doing amazing things with little funding and this boost would help to speed things up and give families the hope they need."
The petition has gained in excess of 100,000 signatures in just three weeks, and has been debated in parliament.