Reality TV show Wife Swap, in which women switch husbands and families, has picked up almost two million viewers in two weeks after becoming a word-of-mouth hit.

The Channel 4 show was watched by 5.7 million people on Tuesday - up from the 3.9 million who saw its first show two weeks ago.

Wife Swap is one of Channel 4's most popular shows

In contrast, BBC One's high-profile army series Red Cap, starring former EastEnders actress Tamzin Outhwaite, has lost almost one million viewers in the same period.

A new series of Wife Swap has already been commissioned and a pilot episode of a United States version will be made.

Wife Swap became a national talking point after the first episode, in which a woman who was against mixed race relationships was put together with a sexist black man, resulting in heated arguments.

On Tuesday's show, a mother with six children and a mother of one swapped families for a fortnight.

The episode's viewing figures of 5.7 million put it ahead of Red Cap, which was watched by 5.5 million.

US version

Both were beaten by a James Bond film, The World Is Not Enough, which was seen by an average of 7.6 million on ITV1.

Wife Swap has become one of Channel 4's most popular shows of the past year, after Big Brother and Jamie's Kitchen.

A pilot show will now be made for the ABC network with the prospect of a full series of a US version.

The final episode of the current Channel 4 series will be shown on Tuesday 28 January.