Speaking during the Royal Television Society conference in London, he said the broadcaster would not be able to compete due to licence fee cuts.
He urged people to support the BBC in an age of “fake news” and “decreasing British content”, as Amazon and Netflix continued to expand their audience share.
Lord Hall, 67, said: “While it looks likely other companies are taking over nationally, the BBC has had its funding cut.
“We need to find more money. The public doesn’t like cuts – it’s their BBC and they want more from it, not less.”
“What we currently do is not sustainable with the pressures we face.”
Lord Hall cited the loss of BBC3 and Formula 1 coverage as signs of the Beeb’s weakening position.
He also stressed the need for a trusted public service broadcaster to battle the disinformation “undermining our democracies”.
And he said despite reducing company running costs to just six per cent, the BBC would need to spend more “just to stand still”.
