The CAA is proposing a new, more transparent framework for air seat allocation after its research concluded that having to pay to sit together was one of passengers’ biggest concerns.

Its review found consumers were collectively paying between £160 million and £390 million a year for allocated seating, between £74 million to £175 million of which is being spent “unnecessarily” in so much as these passengers would have been seated together automatically.

While prices started from £1.99 and generally range from £5 to £30 per seat, the CAA found some airlines were charging up to £100 for certain seats.

All 10 of the UK’s top 10 airlines, based on passenger numbers, confirmed they had received complaints about allocated seating - with one airline receiving almost 3,000 complaints last year.

The CAA surveyed nearly 15,000 adult passengers, more than 4,000 of whom had flown as part of a group over the past year.

Some 87% were aware airlines might not automatically allocate seats together while around half of respondents believed airlines would do their best to sit people in a group together.

However, the CAA found seating policies varied between airlines operating in the UK, meaning those flying with some airlines were more likely to be separated from their group than with others.

The CAA’s three key concerns were over passengers with reduced mobility being separated from carers, families with children where parents are separated from their youngsters, and transparency, with there being a general lack of understanding of the likelihood of being split up, leading to some paying fees despite the “low” chance of being split up.

Tim Johnson, CAA policy director, said: “The practice of charging for allocated seating has clearly become part of airlines’ pricing strategies, which can impact especially on certain groups, such as those with accessibility needs and those travelling with young children. We are also concerned about how transparent and easy it is to compare prices and make an informed buying decision.

“Today, we are proposing a new framework, following engagement with stakeholders, which will be used to assess airline seating practices. This includes transparency, options to add information about travelling with children, older people and those with accessibility needs.”

Liz Sugg, UK aviation minister, added: “Passengers rightly expect to be charged fairly for services and allocated seating is clearly a concern for those flying. This report shows the Civil Aviation Authority is making good progress in working with airlines to ensure that seating practices are as transparent as possible.”

The CAA has pledged, over the coming months, to work with airlines to explore how to make prices clearer and more transparent, and work with other regulators on the use of allocate seating algorithms.