Downing Street has said striking workers can not be given “double-digit pay rises”.
Border Force staff, railway workers and driving instructors took industrial action on Wednesday over pay, jobs and conditions.
But Rishi Sunak’s spokesperson said big salary increases would “embed inflation”.
“We want the strikes to come to an end, we want people to agree a fair pay settlement but, as we’ve said before, what we can’t do is allow for double-digit pay rises,” the prime minister’s spokesperson added.
According to the Daily Mail, rail union and industry bosses “nearly there” in reaching a deal, but No.10 would not be drawn on the report.
Public and Commercial Services union (PCS) members working as Border Force officers at Gatwick, Heathrow, Birmingham, Cardiff, Manchester and Glasgow airports and the port of Newhaven resumed strikes on Wednesday for four days.
Driving examiners and local driving test managers also launched a five-day strike, with the walk-out involving PCS members in 71 test centres in eastern England and the Midlands who are employed by the Driver and Vehicles Standards Agency (DVSA).
West Midlands Trains said that none of its services would be running from Wednesday morning as a result of 24-hour Transport Salaried Staffs’ Association (TSSA) strike action.
Great Western Railway warned of disruption as TSSA members walked out from 12pm until 11.59am on Thursday.
PCS general secretary Mark Serwotka said of the examiners’ strike: “Our members have been offered a pay rise of just 2% at a time when the cost-of-living crisis is above 10%.
“We know our action will cause widespread disruption and inconvenience to people in eastern England and the Midlands – hundreds of driving tests have been cancelled already in other parts of the country – but the Government is to blame.
“These strikes could be called off tomorrow if Rishi Sunak and Jeremy Hunt put some money on the table.”
Meanwhile, unions are reportedly looking at ways to stage further strikes by splitting ballots by job titles rather than holding a single vote.
It comes after a day of travel chaos despite a rail strike by the Rail, Maritime and Transport Workers’ Union (RMT) coming to an end, with crowds of people left waiting at major train stations across London and many journeys delayed due to the late handover of engineering works.