Customer engineers at HP are striking on Monday after deciding to take action over the loss of benefits.
Members of the Unite union voted in favour of strike action last month after HP transferred their jobs to another HP company, HP CDS. The union says the company is "taking advantage of weaknesses in current employment legislation to remove pay and pension benefits".
The benefits lost include a performance bonus scheme up to £2000 and the final salary pension scheme.
Workers will also strike in the new year, with two day strikes planned for 11th and 12th January, 1st and 2nd February, and five days planed for 22nd to 26th February.
There is also a continuous overtime ban and work to rule from 4th January.
Unite says HP has failed to engage with either the union or the conciliation service ACAS over the dispute.
Andy McDowall, Unite regional officer, said, "The members have had an irreplaceable pension benefit removed by a cash rich employer when they had every opportunity to allow it to continue. To add insult to injury, they have also removed our members' contractual bonus arrangements resulting in a further cut in wages.
"This dispute would be relatively easy to resolve, if HP would agree to sit down with us and talk with us. We urge them to return to the negotiating table."