Lancashire business chiefs have urged Transport Secretary Chris Grayling to step in and end “damaging” train strikes.
The North & Western Lancashire Chamber of Commerce has called for a solution to the dispute
The RMT union is continuing weekly action in a dispute with Northern over “driver only” trains.
Babs Murphy, chamber chief executive, said in her letter to Mr Grayling that she was concerned about the decision to continue Saturday strikes by staff until December 29.
She said: “I write to you with some considerable anger and frustration at the ongoing industrial dispute between Northern Rail and the RMT Union.
"As I am sure you are aware, RMT members have been staging one-day strikes on Saturday since September, which were due to finish on November 10.
"However, they have now announced extra dates running from November 17 to December 29 – all of which are Saturdays.
"This will have a significant impact on routes between towns and cities across our region in the run up to Christmas – and we are extremely concerned about the potential damage this could have on town centre businesses who have already endured a difficult year.
"The strikes are not just damaging for trade but also impact on people getting to work, causing misery for employers and employees alike.
She added: "Frankly, we are not particularly interested in the rights and wrongs of the dispute.
"What we need is an immediate resolution to this protracted saga and we urge you to exert all of your influence on the parties involved to bring about a settlement."
The strike action, together with some cancellations on Sunday , will see Northern running reduced timetables across the weekend.
RMT General Secretary Mick Cash said:“RMT continues to make every effort to get serious and meaningful talks going with Northern but the company are not interested and would prefer to continue to bury their heads in the sand regardless of the impact on the travelling public".
Northern says modernisation of its fleet and working methods are essential.