A nuclear fusion start-up backed by Amazon founder Jeff Bezos has raised $100m to help develop its technology and build a demonstration power plant.

Canada's General Fusion hopes commercialise the technology to harness energy that is released in the centre of stars or in a hydrogen bomb. It relies on fusing small atoms together into smaller ones.

In theory, the process could release huge amounts of energy. For now it remains in the research phase with significant scientific and technical challenges.

General Fusion secured backing from Singapore's Temasek and Canada's Strategic Innovation Fund as well as the backing of Mr Bezos. It raised $100m in the new funding round and brought its total backing to more than $200m. Other investors include Microsoft.

Cracking nuclear fusion promises a near infinite supply of cheap, carbon free energy, while producing far less nuclear waste than during fission, the process used to power conventional nuclear power plants.

By fusing hydrogen together atoms under heat and pressure, a fusion reactor would create the heavier atom helium, releasing energy. The energy is theoretically safer and cleaner than regular nuclear reactors, but it requires large amounts of energy to create superheated plasma. This is achieved using a giant device called a tokamak that holds the plasma in a magnetic field.