The tech firm, which has made the ChatGPT chatbot, has surged in value as investors including Microsoft continue to be fascinated by artificial intelligence (AI).

OpenAI's value is similar to the investment bank Goldman Sachs and is more than the majority of the biggest companies in the US – meaning that it is one of the most valuable start-ups on the planet.

The firm says that the cash will enable them to remain at the forefront of research into AI.

OpenAI said: "The new funding will allow us to double down on our leadership in frontier AI research, increase compute capacity, and continue building tools that help people solve hard problems."

The latest funders include the investment firm Thrive Capital, US chip behemoth Nvidia and Microsoft – which already has a large stake in the start-up.

OpenAI's chief financial officer Sarah Friar suggested that the investment was down to the popularity of ChatGPT – which has over 250 million active users per week.

She said: "Every week, over 250 million people turn to ChatGPT regardless of the scale of the challenge – whether it's communicating with someone who speaks another language or solving the toughest research problems. AI is already personalising learning, accelerating healthcare breakthroughs, and driving productivity. And this is just the start."

The cash injection comes as OpenAI has been in the headlines for internal leadership conflicts – with some staff unhappy at chief executive Sam Altman's decision to restructure the company so it becomes a for-profit entity.

Co-founder Elon Musk left OpenAI in 2018 and has accused the firm of abandoning its initial mission of developing AI for the human race's benefit.