The boss of beleaguered Arriva Trains Northern has appealed for workers to consider its latest pay offer to try to prevent a series of new strikes.

And Euan Cameron, Arriva's managing director, has complained to the Rail, Maritime and Transport Union about the tone of a letter it has sent out to its members which says: "Accept Arriva's present offer and you will regret it for the rest of your railway career".

Today Mr Cameron said: "We have written saying it is totally unacceptable and saying back off.

"We have a very strict code of conduct on this and would take any necessary action."

But Stan Herschel, regional organiser for the RMT, said the complaint was baseless - and all the bullying and intimidation had come from the company's side.

He said: "The complaint was about one sentence from a note, and we said that if you accept it you would regret it because it is second best and you deserve more.

"They are saying that we are threatening people with physical violence and that's rubbish. As far as we see it, all the bullying and intimidation has come from them.

"I have seen female workers in tears and male workers being physically sick through worry."

Mr Cameron said it was vital for the workers to be balloted on the company's latest four per cent offer but claimed the union had dismissed the offer without consultation. He said failure to accept the offer would mean the loss of £2,500 a year to staff and he added: "If they are losing that amount they should have a say."

Mr Cameron also claimed the union had not co-operated with moves to go to arbitration.

He spoke out as an eight month period of disruption loomed for fed-up passengers. The next stoppage is expected to be confirmed for Friday.

Workers are expected to stage a programme of ten, one-day strikes aimed at disrupting major bank holidays and special occasions like the opening of the Commonwealth Games in Manchester due to be attended by the Queen. The opening of refurbished Leeds station by Prime Minister Tony Blair is also likely to be hit.

Mr Cameron said the company was seeking to minimise the effect by training managers to drive, but he stressed passenger safety was paramount.