The SWT price hike has been condemned as "excessive"

The rise on South West Trains (SWT) from Sunday affects services coming into London after the rush-hour "peak".

The Liberal Democrats have tabled a Commons motion condemning the increase as "excessive" and calling for a review of the regulation of rail fares.

Transport Secretary Douglas Alexander has said he is limited in what he can do as only peak fares are regulated.

The SWT rise means passengers will not get off-peak discounts until much later in the morning.

No case

Mr Alexander told the Commons on Tuesday: "The fares at off-peak times are not regulated fares.

"Although I understand that there was real concern and public interest in the fares that were announced, it is important to emphasise that that those are not fares set by government.

"There must be a degree of flexibility for train companies to set prices against other modes of available transport, but I would urge all train companies to act responsibly when considering the setting of unregulated fares."

David Laws, the Lib Dem work and pensions spokesman, who has tabled the motion, said the company had failed to "provide an adequate business case" for the decision.

However, SWT has insisted that the new prices will bring the company into line with other operators and allow it to "better match demand and pricing".

Examples of the increases, which were first announced in March, include a cheap day return from Alton, in Hampshire, to London rising from �15.80 to �19 - a 20.25% increase.

A Bournemouth-to-London cheap day return will go up from �36.40 to �43.70 - a 20.05% rise.