Budget airline Ryanair is to force passengers travelling with young children to pay a £4 seat reservation fee on any flights booked after 1 September, in the latest development in the ongoing row over whether parents should be able to sit next to their kids on flights for free.

Last year MoneySavingExpert.com launched a campaign demanding that budget airlines scrap the 'family tax', where many airlines refuse to guarantee families a seat together and worried parents end up forking out for a reserved seat just to have peace of mind.

But Ryanair's now taken this a stage further and become the first airline to make paying for a seat reservation compulsory for at least one adult travelling with children. Other adults in the group can choose not pay; they just may not get seats next to the rest of the group. See our Budget Flight Fee-Fighting guide and 20 Ryanair Tips for more pricey 'extras' to watch out for.

How will the charge work?

On Ryanair flights booked from 1 September, at least one adult in every booking which includes children under 12 will have to pay £4 for a reserved seat at the time of booking. All children under 12 in the same booking will receive free reserved seats next to the adult.

Additional adults or children aged 12 or over also have to pay £4 to reserve a seat. They can choose not to pay and be assigned a seat free of charge, but if they do this, they may be seated away from others in their group.

The fee is per passenger, per flight. So, for example, if a family with two parents, a teenager and an 11-year-old flew to Europe and back and wanted to sit together, they'd potentially need to stump up an extra £24.

The announcement is likely to anger many young families who feel parents should be guaranteed a seat next to their children at no extra charge.

Ryanair doesn't allow separate bookings for children under 16, so unfortunately there's no way round this – if you're flying with kids under 12, you will have to pay for a seat reservation.

Why has Ryanair introduced the charge?

Ryanair says "boarding issues" are to blame for the new policy – it claims cabin crews have been forced to reseat passengers because "many adults travelling with young children did not select reserved seats and accordingly were randomly allocated seats that were not together".

The company adds that it can't move customers who'd paid for allocated seats "to simply accommodate other customers who are travelling with young children, who declined to reserve their seats and chose to have randomly allocated seats".

What do other airlines do?

While Ryanair's the only airline to have so far made paying for a seat reservation compulsory, many airlines will refuse to guarantee that parents will be able to sit with their children unless they pay a fee, as the table below shows:

How much do airlines charge to pre-select your seat each way?

Easyjet Yes £1.99 – £6.99
Flybe No From £6.50 ('Just Fly' ticket)
Jet2.com Unclear (i) From £4
No From £3 – £11 (scheduled flights)
Ryanair No £4
Thomas Cook Yes From £7
Thomson/ First Choice Yes (ii) £7 – £15 (iii)
Prices correct as of 3 Aug 2016. (i) It told us: "We give priority to those travelling with children to ensure that they are seated together. However, for family groups wishing to select specific seats or seating configurations, there is a small charge." We're clarifying exactly what this means. (ii) It told us: "We always try to seat customers travelling together next to each other wherever possible, with priority given to families travelling with children". It adds: "If a customer has chosen not to use the pre-booking service and, in very rare circumstances, their child is initially allocated a seat away from them, it will be re-assigned". (iii) Child prices (to select a seat) are £3 – £7.