A WAREHOUSE in Dartford being used to store undelivered mail now contains an estimated 15 million items, according to the Communication Workers’ Union.

The union says the Royal Mail outhouse in Sandpit Road is continuing to fill up with a backlog of post since it opened last month, as a result of postal strikes and lack of room in sorting offices around London.

It says the building is the size of an "air hangar" and could fit several aircraft inside.

Two weeks ago the union estimated around four million items were being stored, but now the figure appears to have dramatically increased.

However the Royal Mail says a figure of 15 million is "nonsense" and that the backlog nationally stands at four million.

A spokesman for the union said: “I would say there are in excess of 15 million items.

“Once you get above 15 million it’s difficult to do any sort of genuine science on it.

“There’s a sea of yorks (trolleys to carry mail) in there and it becomes virtually impossible to calculate, but it’s massive.”

The spokesman also says that clearing the backlog would take up to four weeks.

He said: “Royal Mail say they are one day away from clearing the backlog, and if they are one day away I am the tooth fairy.

“We want a resolution to this issue, and the only way there’s going to be a resolution is by management, the government and the union, all getting round the table.”

The union says around 100 agency staff are being employed per shift at the minimum wage of £5.80 an hour to sort post.

Its members last week voted in favour of a national strike in a bitter row over jobs, pay and services.

This threatens to further disrupt deliveries in the coming weeks.

Royal Mail’s managing director Mark Higson said: “We have held more than 70 meetings with the CWU over the last few months and we call on them now to stop the strikes, get back round the table and talk."