The 16pp colour leaflet, called Why the Government Believes That Voting to Remain in the EU is the Best Decision for the UK, will be sent to 27 million homes and sets out the reasons why the government supports a vote to stay in the EU. It is also available to view or download from the accompanying website.

The campaign has cost £9.3m. £5.9m went on printing and delivery costs and £2.9m had been spent on the accompanying website and digital promotion. Production of the leaflet made up £458,500.

The government has not responded to requests for information but PrintWeek understand the 27 million leaflets were procured via Williams Lea, which holds the HMRC Print Vendor Partner contract with the government.

The print could have been given to any of the firms on its roster, believed to be DST Output, The Lettershop Group, Howard Hunt, GI Solutions, Eclipse and Anton Group. Polestar Group was previously understood to be on the roster but that may have changed following its pre-pack administration.

The campaign has been slammed by Vote Leave supporters. Vote Leave has branded the leaflets “propaganda” and complained that tax payers’ money was spent on them. Vote Leave supporter London Mayor Boris Johnson called them “a crazy waste of money”.

But speaking on BBC Radio 4's The World Tonight last night, Britain Stronger In Europe campaign group board member Damian Green said: "People have been crying out for facts. The government has produced a factual leaflet. Both sides will get a leaflet funded by the Electoral Commission during the actual period itself. That's what's fair."

DST Output client experience director Nick Barbeary said the decision to focus on a leaflet campaign “supports the view that print still has a part to play in being a relevant communication channel not only now but into the future”.

He added: “People are getting tired of their inbox being cluttered, print is not seen as being as invasive as email or text by the user.” He said the beauty of print was that it remained in people’s houses and they would be more likely to read it later when they had time.

The Private Life of Mail, a report based on 18 months of in-depth research into the role mail plays in people’s lives found exactly this. Door drops stayed in people's homes for 38 days on average, the study found. The research and the report was commissioned by Royal Mail, which is delivering the leaflets.

Barbeary added: “Mail interacts with other channels when it’s done right. The government is using all the tools at its disposal.”

The Lettershop Group joint managing director Dave McGolphin agreed.

“It’s good for print, although they are spending quite a lot on the website too. Print is the most effective way to get the message across,” he said.

“If you want to get a message across that’s quite complex, you want people get that message in written form and consider it. I would have said that print is a far more effective way of doing that than an email.”

He confirmed that Williams Lea was a customer but did not comment on whether his company had printed any of the leaflets.

Another supplier GI Solutions Group also said it was not able to comment.

Referring to the Royal Mail research, GI chief executive Patrick Headley said research found that people did not read emails and information about the EU Referendum was too important to be overlooked.

“Everyone needs the facts about what it will mean. If you want to get a message out to people then the printed media is the way to get it.”