The donation, from a supporter who wishes to remain anonymous, will be paid in instalments over the next six years and will be used to finance research into the disease.
It is more than double the organisation’s previous highest gift of £1m, pledged by a single donor after hearing the charity’s president, MP Lembit Opik, call on the Prime Minister in Parliament to increase funding for research into the condition.
MNDA is bidding to raise £7.5m to finance research into motor neurone disease through its research foundation, alongside a campaign to persuade the Government to stump up an equal amount of funding. The latest pledge puts the total raised at almost £4m.
MNDA research director Brian Dickie said: “This enormously generous donation takes us a significant step closer to achieving our goals of understanding the causes of motor neurone disease and of finding a cure.”
There is currently no effective treatment for MND. Five people a day die from the disease in the UK and it kills 100,000 people across the world every year.
Earlier this year, MND returned a £100,000 gift from the Stone-Mallabar Charitable Foundation after it insisted the donation was spent on a specific project the association said was "not consistent with its strategic objectives".