Almost 4,000 complaints were made against UK airlines last year amid warnings that carriers were hiding behind red tape to deny passengers their rights.

Objections over delayed flights, cancellations, lost bags and being ‘bumping off’ – when passengers are forced off overbooked aircraft – were made to a new watchdog.

The complaints were made during the first 12 months of a system that forces airlines to offer passengers the right to an independent appeal when they think that they have been badly treated.

The new body, which covers British Airways, EasyJet, Thomson and Thomas Cook, warned that companies were using baffling terms and conditions to confuse passengers.

In its first annual report, the body said that airline rules should be “written in plain English and easy for consumers to understand”.

Under rules set up by the Civil Aviation Authority, airlines are supposed to offer passengers recourse to an appeals body to rule on major complaints.

The biggest UK-based airlines refer passengers to the Centre for Effective Dispute Resolution (CEDR), an independent mediation group in London.

In its first annual aviation report, the body said that it received 3,842 complaints in the year to the end of January 2017. Of those, 2,826 were related to delays and 508 to cancellations.

A further 126 complaints were about so-called “denied boarding”, when airlines bump passengers off overbooked flights, while ten were made over downgrading to a worse seat.

In its report, CEDR said that airlines’ “conditions of carriage are not always as clear and watertight as they could be, which leads to disputes,” The Times reported.

Alex Neill, managing director of home products and services at consumer group Which?, said: “Passengers who have faced disruption and may have had travel plans thrown into chaos shouldn’t have to jump through hoops to work out what they are entitled to.”

BA said: “Our terms and conditions are in plain English and clearly displayed on during the booking process.”

EasyJet said that it “provides clear and easily accessible information for customers to ensure they fully understand their rights”.