Royal Mail workers have voted to strike for the first time since it was privatised four years ago in protest over pension changes.

Members of the Communication Workers Union (CWU) backed walkouts by 89 per cent on a turnout of 73 per cent of the 110,000 balloted.

Terry Pullinger, the union’s deputy general secretary, said: “This ballot result is hugely significant and demonstrates a strength of feeling that can only be translated as a massive vote of no confidence in the managerial leadership of the Royal Mail Group.

"They have failed and should resign or be sacked.

“This is a dispute about honour and we refuse to simply stand aside.”

The workers can strike in the next six months, which has led to concerns about the impact it could have on Christmas deliveries.

David Jinks head of consumer research from rival parcel firm ParcelHero, told the Sun: "For some families, the timing of any strike or work to rule could mean that Christmas is cancelled by this action.

"If industrial action goes into the seasonal period it will have a huge impact.

"Even if the strikes are limited; it will have significant consequences across the industry as other delivery companies try to absorb the extra volumes at this hugely busy period."

A Royal Mail spokesman said: "Since privatisation, Royal Mail has paid £1.4 billion into employees' pensions. In the same period, Royal Mail has paid £800 million in dividends to shareholders, including colleagues."

They added it was "very disappointed" about the planned strike action.

"Royal Mail is committed to further talks as a matter of urgency, to reach agreement with the CWU. There are no grounds for industrial action.

"In 2013, Royal Mail and the CWU committed to the Agenda for Growth (AFG) - a legally binding agreement. Royal Mail has brought to the CWU’s attention the contractual dispute resolution procedures included in the AFG, which both sides are required to follow once instigated.

"They escalate to independent external mediation, which we expect will take close to Christmas to be completed, and may be longer. We believe these dispute resolution procedures must be followed. The union cannot take industrial action until they have been completed.

"Industrial action is damaging for our business. It undermines the trust of our customers. It makes it harder to pay for the great terms and conditions we provide for our employees. National industrial action means the current offer from Royal Mail, including on pensions, will be taken off the table."