It will mean an end to the "too good to be true" billboards boasting of 1p trips to exotic ports of call throughout Europe.

More than half of online customers do not realise there is a wide variety of price bandings for the same route.

Consequently passengers end up paying well over the advertised fare.

The OFT move follows its own investigation in February of this year into some airlines which, it is claimed, were failing to add mandatory taxes onto advertised fares.

It ordered all the airlines to get their houses in order, but yesterday it reported that a few of them are still not complying.

Amongst the charges that have not been included in adverts are government taxes, air passenger taxes, and security and fuel surcharges.

Last night, Ray Hall, a spokesman for the OFT, said the pricing policies of some firms were still "leading consumers to make the wrong choices".

"We have given the airline industry a deadline to make change - some have complied and some have not," he said.

The OFT has the power to take firms to court and order them to change their polices if they do not co-operate with it.

Its stance was supported by the Association of British Travel Agents (ABTA). A spokesman said: "The days of the 1p flight have now gone, but in reality they were never here."

The demand for change was also backed by the Air Transport Users Council (AUC), which estimates that just 47% of travellers who booked flights online were aware that there were different levels of taxes and charges for the same routes.

In one example it provided, a family of four flying to Palma was quoted £319.92. When additional charges were taken into consideration, that price rose by almost 50% to a total of £479.56.

No one is named in the OFT report, but according to the BBC, which carried out its own investigation into airfares, several low-cost airlines are continuing to advertise fares without adding on taxes.

No one was available for comment from the airlines last night.

However, reacting to the BBC claims, a spokesman for easyJet said that it had implemented changes that would mean that by the end of the summer all the prices given out on its website would include taxes and charges.

The firm had already ensured that this was the case on its billboard and press adverts.

Ryanair said all its website prices on its home page already included extra costs, and it would be changing the other parts of its site by the end of the year in order to make it comply with the regulations.

Flythomascook also confirmed it would be making the required changes by the end of next month. Jet2 said it was currently in talks with the OFT to try to work out the best and quickest way to implement the necessary changes.