Rail passengers are being warned to avoid travelling on Saturday unless “absolutely necessary” as further walkouts are set to cause disruption.

Network Rail said the Christmas Eve strike by its workers in a row over pay would have a severe impact on services.

Trains will finish at around 15:00 before RMT union members begin industrial action at 18:00.

In the latest strikes in the run-up to Christmas, postal workers and Border Force staff are also walking out.

Around 1,000 Border Force workers began strike action on Friday at Heathrow, Gatwick , Manchester, Birmingham, Cardiff and Glasgow airports, as well as the Port of Newhaven.

Border disruption has been minimal, with military personnel and civil servants being drafted in to cover strikers.

Heathrow Airport said operations were running smoothly on Saturday. A spokesperson added: “The immigration halls are free flowing with Border Force and the military contingency providing a good level of service for arriving passengers.”

Border Force personnel will be striking until the end of the year – with the exception of 27 December – but there are warnings strikes could last for months unless a new pay deal is negotiated.

Meanwhile industrial action at Network Rail, which maintains the UK’s rail system, will continue until 06:00 on 27 December.

Network Rail said there would be “significantly reduced services across the rail network on Christmas Eve”.

Last trains on long-distance routes will depart much earlier, with some rail companies unable to run any services at all.

The last train times on major routes include the 09:45 from Leeds to London, the 11:22 from London to Edinburgh, and the 12:48 from London to Manchester.

“Only travel if absolutely necessary on Saturday 24 December,” said Network Rail.