Can we travel on a passport with less than 6 months validity?

It is possible to travel on a passport with less than 6 months validity. Providing the Passport/ID card is valid for both the outward and return leg of the journey you are able to travel with less than 6 months left on the Legal Document.

Other Documentation Information

Irish Sea

For travel between Eire and England, photographic identification is required for all passengers (including children and infants) as they may be asked to prove citizenship at any time.
Larne - Cairnryan & Larne - Troon routes, photographic ID is not required.
On all POIS routes, senior citizens and students must provide proof at check-in (eg student ID card) not to incur an increase in fare.

All Other Routes

Valid full 10-year passport or National Identity Card is required.

 From 17Jun09, all members of the EU must have a valid national identity card or passport (with photo) to travel into the UK.

 Driving licenses, "Livrets de Famille" for infants will no longer be accepted.  Members out of the EU must have a valid passport.

For French nationals, the extension to an expired ID card will not be accepted for entry into Belgium.

Visas

Non-EU members are advised to speak to their embassy regarding other relevant information, such as Visas.

 Useful Visa Services information can be found at http://www.ukvisas.gov.uk

 For passport and visa enquiries, passengers can contact the UK Border Force helpline: 0843 308 8259

ID Cards

This scheme has now been scrapped by the new government.  Existing cards can still be used as a valid identity document for travel within Europe.
 
The new UK National Identity Cards are valid on all routes and can be used in place of a passport when travelling within the EU/EEA and Switzerland.  However, UK Identification Cards are not valid for travel and do not provide proof of nationality.

For more information use the following links:

UK National ID Card information
UK ID Cards - What to look out for - a guide to the identity card's security features