Aslef said drivers on First North Western will walkout every weekend from September 28-29 to November 23-24, in an escalation of a long-running dispute.
The first 48-hour stoppage will affect delegates, and possibly government ministers, travelling to Blackpool for the Labour party conference, which opens on Sunday September 29.
The drivers have already staged a number of 48-hour strikes which hit weekday services, causing huge disruption to commuters and other travellers.
Aslef's general secretary, Mick Rix, said today: "We have decided to set weekend strike dates in order to minimise disruption to commuters and to let the public know exactly what service may be expected."
The union's executive also decided today that the drivers will stop all rest-day working from the end of the month.
Mr Rix is to write to strategic rail authority (SRA) chairman, Richard Bowker, seeking an urgent meeting to try to resolve the dispute.
The union leader said there was no chance of the dispute being settled while First North Western (FNW) had its "hands tied" by the SRA over what it could offer.
The company said it had made an offer of a 19% pay rise over three years which was "beyond the dreams" of many workers.
Aslef claimed the company was trying to attach unacceptable "strings" to the offer.
Many delegates to Labour's conference plan to fly to Manchester airport and catch a FNW train to Blackpool, partly because of disruption to trains out of London's Euston station at weekends because of engineering work.
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