Since the twins turned two, I've done nothing but complain. Whereas once we used to occupy just three plane seats between the five of us, now we have to book (and pay for) the full family complement. Then there's the added cost of having to take two rooms rather than just one, as a so-called family room often means beds for a maximum of four.

But it would be far worse if there were just two of us - one adult and one child. Then it would be really expensive to go away. Reader Jacqueline Evans writes, "I'm a lone parent, trying to organise a holiday where there are activities and clubs provided for little ones. Unfortunately, I'm having difficulty finding one where I don't have to pay adult prices for my three year old simply because there aren't two adults in our party."

This is a common problem; most package deals are based on two adults sharing a room. If it's just you and a toddler, the toddler has to pay full price. And special offers aren't always all that special: reduced or free child places often aren't available to one adult travelling alone.

Some operators, realising at last that nuclear is no longer the norm, offer one-parent deals (if only at selected hotels), including Thomson Skytours (thomson-holidays.com) and Virgin Holidays (virginholidays.co.uk). More modern-minded Mark Warner (markwarner.co.uk) and Neilson activity holidays (neilsonstore.com) never charge a single supplement; Neilson even gives a discount on flotilla holidays to lone parents. The National Council for One Parent Families (freephone 0800 0185026, oneparent families.org.uk) issues a free holiday guide, which includes all sorts of tips.

It's still shocking that any commercial companies are allowed to discriminate against lone parents. When a tour operator advertises family holidays, it should mean any family - mine or Jacqueline Evans's. A family's a family, whatever its size.