By Evan Davis Economics editor, BBC News

There has been a big rise in flat construction in recent years

The prices of flats in most parts of England and Wales are not keeping up with those of houses, according to figures from the Land Registry.

The figures suggest that outside London, flats enjoyed a bigger surge in prices over the past decade than houses, but are now underperforming.

In the first quarter of 2007, flat prices in nine out of 10 regions fell below those of houses.

And flats in those areas are often falling in price in real terms.

Over supply?

One explanation might be that the supply of flats has grown enormously over the last decade.

In England, only about one in six dwellings is a flat - but of new-built properties, it's not far short of one in two.

Developers say they are building a lot of flats because they are being encouraged to develop brown field sites with high density accommodation.

However, in a few cities the supply of new flats may be causing problems.

Unoccupied city centre apartments are now sometimes being let for one or two night stays, in competition with hotels.

The phenomenon of the market for flats does not show up in the national Land Registry price data released to the press each month, because the overall figures are hugely affected by London where prices of everything have been rising fast.

Earlier cycle?

Once the London effect is taken out, the slowdown becomes more apparent.

It is striking that the price of flats soared ahead of those for houses until the past year; in the Yorkshire and the Humber region, flats rose 180% between 1997 and 2005, while house prices rose 154%.

In the last year though, flats in that region have fallen by 3%, while houses have risen by between 5% and 10%.