Royal Mail workers and university lecturers will continue with a strike on Friday in long running disputes over pay, pensions, jobs and conditions.
Members of the Communication Workers Union (CWU) and University and College Union (UCU) walked out on Thursday for 48 hours, with more action planned in the coming weeks.
Picket lines were again mounted outside universities and Royal Mail centres across the country on Black Friday - one of the busiest shopping days of the year.
It comes as the Royal College of Nursing (RCN) announced its members will stage their first ever national walkout on December 15 and 20.
UCU General Secretary Jo Grady said 70,000 university staff were on strike on Thursday, adding: “They will no longer accept falling pay, pension cuts, brutal workloads and gig-economy working conditions. If vice-chancellors doubted the determination of university staff to save our sector then today has been a rude awakening for them."
She said staff were "overwhelmed" by the support of students who joined them on the picket lines yesterday.
She added: "Our members deserve a proper pay rise and the money is there to deliver it. Vice-chancellors now need to urgently address the concerns of staff otherwise our 70,000 members will escalate this dispute into next year.”
University employers said they were taking steps to mitigate any disruption adding that the union was seeking an “unrealistic” 13.6% pay rise which would cost institutions around £1.5 billion.
The CWU has rejected Royal Mail’s final offer and is pressing ahead with more strikes, including today and on Christmas Eve.
A CWU spokesperson said: “Millions of customers and thousands of small businesses rely on the quality services Royal Mail workers provide at Christmas.
“But Royal Mail bosses are ignoring those responsibilities and ploughing ahead with plans that would wreck the livelihoods of their entire workforce.
“We call on the government, media and all small businesses to demand that Royal Mail takes a mature approach to this dispute."
“Thousands of workers aren’t striking at Christmas for fun – they want to reach an agreement."
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