It comes as members of the Rail, Maritime and Transport (RMT) union began their latest strike, whilst physiotherapists in England and Wales also voted to go on strike in a dispute over pay and working conditions, in a move announced by the Chartered Society of Physiotherapy.

Nurses in England, Wales and Northern Ireland are also set to strike on Thursday unless there is a breakthrough in Government talks. However, there were no talks between Health Secretary Steven Barclay and the Royal College of Nursing (RCN) scheduled after they fell apart on Monday.

Royal Mail workers across the country, including at the busy Leeds Mail Centre, mounted picket lines outside sorting and delivery offices.

Royal Mail vehicles at Leeds Mail Centre in Leeds, as Royal Mail workers go on strike in the increasingly bitter dispute over jobs, pay and conditions.

The two sides have held talks in recent weeks but the row remains deadlocked.

CWU general secretary Dave Ward said: “Royal Mail bosses are risking a Christmas meltdown because of their stubborn refusal to treat their employees with respect.

“Postal workers want to get on with serving the communities they belong to, delivering Christmas gifts and tackling the backlog from recent weeks.

“But they know their value, and they will not meekly accept the casualisation of their jobs, the destruction of their conditions and the impoverishment of their families.

Members of the Communication Workers Union (CWU) on the picket line outside Leeds Mail Centre in Leeds, as Royal Mail workers go on strike in the increasingly bitter dispute over jobs, pay and conditions.

“This can be resolved if Royal Mail begin treating their workers with respect, and meet with the union to resolve this dispute."

He added: “Posties are facing an outright assault on their livelihoods and dignity, and have no choice but to see this dispute through to its conclusion.

“The reckless, aggressive and bullying attitude from senior managers of this company is now totally out of control.

“When our members take strike action on Wednesday and Thursday, the question every media outlet should be asking is not why they’re striking, but why these people are being allowed to get away with the evaporation of a 500-year-old national treasure.”

A Royal Mail spokesperson said: “The CWU is striking at our busiest time, deliberately holding Christmas to ransom for our customers, businesses and families across the country.

“We are doing everything we can to deliver Christmas for our customers, and would like to thank the increasing number of posties returning to work each strike day, temporary workers and managers from across the business who are helping to keep the mail moving.

“However, this task becomes more challenging as Christmas nears.

“Three weeks ago, we made a best and final pay offer worth up to 9% over 18 months.

“Instead of working with us to agree on changes required to fund that offer and get pay into our posties’ pockets, the CWU has announced plans to ballot in the New Year for further strike action.

“Their misguided belief that further industrial action, in a business already losing more than £1 million a day, will result in an improved pay offer is misleading its members and risking their long-term job security.”

Royal Mail has brought forward the final posting dates for Christmas cards because of the industrial action.

The new last posting dates for arrival for Christmas Day are:

– 1st Class, 1st Class Signed For – December 16

– Special Delivery Guaranteed – December 21

Yorkshire Royal Mail workers begin 48-hour strike as union boss criticises ‘reckless, aggressive managers’