The move follows the introduction of a widely-criticised new timetable.

A spokesman for Passenger Focus said commuters were fed-up with not being able to get on trains and were demanding to know what was going on.

FGW said it was confident the changes would improve the reliability of the service over the next few weeks.

Ed Vaizey, MP for Didcot, Oxfordshire, said it was unbelievable how angry people had become.

"It's just a nightmare. People are losing their jobs over this. They are really angry because they cannot get into work on time.

"Why we can't go back to the original timetable, I don't know."

'Cautious welcome'

FGW said it would run more trains early in the morning.

Customers on the Oxford to Paddington line will see more services and capacity will be increased for Twyford and Maidenhead commuters.

There will be more than 100 extra seats for customers travelling between Frome, west Wiltshire, Bath and Bristol.

Alison Forster, managing director of FGW, said: "We recognise that some elements of the timetable have not met all our customers' needs.

She added that the company would continue to review the timetable introduced in December.

Mike Greedy, spokesman for Passenger Focus, an independent public body to protect passengers' interests, said: "We are giving a cautious welcome to the amendments but we still have serious concerns for the service offered to passengers in the Bristol and Thames Valley area.

The additional services will start on 15 January.