Commuters in the Midlands will face inflation-busting rail fare increases from tomorrow - rises which have been met with fury by a consumer watchdog group.

But the big train companies operating from regional stations have justified the increases of about 4.8 per cent which they claim will help pay for further investment on the railways.

The cost of an annual season ticket from Birmingham New Street to Euston on the Virgin Trains West Coast Mainline service will increase from £7,260 to £7,608.

Fares on Chiltern services from Birmingham Snow Hill to London Marylebone will increase, with season tickets rising from £5,484 to £5,788.

Season tickets on the Arriva Cross Country service from Birmingham New Street to Newcastle will increase from £7,676 to £8,044.

London Midland will be increasing its fares by 4.8 per cent two months after the company took over from Central Trains as the provider of local commuter services.

A yearly season ticket from Birmingham New Street to Solihull is expected to increase from its current price of £540.

A spokesman for Virgin Trains yesterday described the increases as "not extortionate" and promised that the company would channel the extra funds back into improvements to services.

The blow to passengers in the Midlands has been softer than in other areas of the country where fares have risen by more than nine per cent.

But Paul Fullwood, secretary of the West Midlands Rail Passengers committee, said: "I cannot believe that increasing already excessive rail fares by above inflation rates can be justified.

"The rail companies have claimed that the increases will help them maintain performance rates which show some of them achieving 80 per cent punctuality.

"But these rates still mean that passengers with an annual season ticket are facing at least one weekly journey that is going to be late.

"And it is certainly confusing why London Midland can claim that its fare increases are designed to boost investment two months after it secured a franchise on the back of promises for future investment."

A spokeswoman for London Midland said the company had said "loud and clear" in November that it would use fares to increase investment.

The spokeswoman added: "We have only increased fares by the 3.8 inflation rate and an extra one per cent that is permitted by the Department of Transport to allow for growth. This is one of the lowest increases in the country."

The fare increases for cheap day returns in the former Centro West Midlands area will be 3.8 per cent, the spokeswoman added.

London Midland will also be investing £300 million in new rolling stock, station improvements and other initiatives during 2008.

A spokesman for Virgin Trains said: "These rises are not extortionate. They are justifiable taking into account improvements on the railway."

Chiltern said it was investing heavily in improving Leamington Spa station and its hub at London Marylebone.

He added: "Nobody likes putting up train fares but overheads do go up."

Arriva trains, which replaced Virgin Trains on the Cross County route when it was awarded the franchise in July, announced earlier this month that it will not be increasing the price of its popular advance purchase tickets.

Regulated fares such as savers and season tickets will increase by an average of 4.8 per cent.

However unregulated fares such as standard and first class open tickets will see increases averaging seven per cent. n Passengers heading to and from Birmingham on the West Coast Mainline faced further delays as engineering works at Rugby continued yesterday and again today.

They went from Birmingham International to Northampton by coach, extending their journeys by an hour. Normal service will resume tomorrow.