Thomas Cook has filed for chapter 15 bankruptcy protection in the United States as the company seeks to safeguard itself from legal action by debtholders.

The struggling tour operator earlier this week delayed a decision on a £900 million rescue deal designed to keep it afloat over the winter.

Fosun Tourism Group has agreed to contribute £450 million of new money to the group.

If agreed, the Chinese conglomerate would acquire 75 per cent of the Thomas Cook airline and up to 25 per cent of the tour operator.

Debtholders and lending banks would inject another £450 million.

The United States filing gives UK law primacy over the bonds held in the US, which should allow it to proceed with its planned restructuring.

Shares in the 178-year-old tour operator have fallen more than 80 per cent since it announced the sale of its airline in February.

The airline is no longer for sale due to the restructuring process.

Fosun currently owns 18 per cent of Thomas Cook.

Shares in the tour operator closed at 4.5 pence on Tuesday.