A war of words has erupted between two rival rail firms over allegations of staff poaching.

Connex has been attacked for sending out letters trying to lure back train drivers who have left to work for Thameslink.

Connex has approached around 50 ex-employees offering them the chance to come back to and benefit from a pay-and-conditions package which "is now among the best in the UK".

Thameslink claimed the move goes against a "gentleman's agreement" not to poach the staff of rival firms. Connex hit back, saying it invested in training for drivers who were then "poached" by rival rail firms. The two companies are competing against each other to win the South Central rail franchise.

A Thameslink spokesman said: "There is a gentleman's agreement in the industry not to approach employees of other firms and offer them jobs and we certainly don't poach drivers.

"They vote with their feet and work with the companies they want to. It is not within the spirit of the gentleman's agreement, as we understand it, to do this sort of thing. But it is for the individuals concerned to make their choices."

The letters read: "Since you left a lot has happened. We have begun an ambitious change programme to deliver benefits for our staff and customers.

"Our pay and conditions package is now among the most competitive in the UK rail industry. In return, we are looking for experienced drivers like you who want to help in turning Connex into one of the best train operating companies in the UK."

The letters also say the firm is working with the union Aslef to bring about a two-hour reduction in drivers' working weeks and offers discounted shares in Connex's parent company, Vivendi.

Connex needs an extra seven drivers for its winter timetable and is spending £8 million training 250 more.

A former Connex driver who now works for Thameslink said: "This doesn't tempt me to go back because I am still quite bitter about the way they treated the drivers."

A similar driver said: "It's absolutely unbelievable and I am very, very cross they are trying to get us back. I wouldn't return for all the tea in China."

A Connex spokeswoman added: "Poaching has been going on for a couple of years. We are the company spending millions of pounds training drivers and then they are lured away by other firms. We are just approaching our former employees to see if they want to come back."