Some travel organisations are imposing “rip-off” charges on customers, Which? Travel magazine claims.

The consumer watchdog magazine looked at the methods of 188 companies, including 51 travel firms and 32 airlines as well as hotel chains and hire companies.

Premium rate telephone contact numbers, “hidden” extras and “free” offers that include payments were just some of the costs uncovered.

It found that 28% of the organisations were using expensive 0871 or 090 calling codes; 43% were adding surcharges or unavoidable booking fees to card payments; 20% were using automatic “opt-ins” where consumers had to untick a box to avoid extra payments for things they may not have wanted; and some offered “free” car hire which was accompanied by an insurance package costing as much as £126.

Ryanair was found to have the most expensive telephone number – at £1 a minute from a landline – followed by Wizz Air (77p), BMIbaby (65p), and Air Malta (both 60p).

Wizz Air imposed the highest charges for use of a credit or debit card, at £7 per person per flight, or £56 on a return trip for a family of four, ahead of Ryanair and Aer Lingus (£6 per person per flight), (£4.50 per person per flight) and BMIbaby (£3.50 per person per flight).

Some operators added on a £2 charity donation to the price of a holiday without giving consumers a say in the matter, the magazine said.

In a separate report, Which? Travel said the London Olympics had sent “hotel prices soaring”.