But the Royal Mail confirmed that there is no way to opt out of the mailshot, meaning all 27million homes in the UK will receive it starting next week.

But last night Mr Cameron stood by his decision saying he would make "no apology" for the leaflet.

He insisted that the Government was "not neutral" in the referendum and the cost was "money well spent".

However, he did admit that the debate in his own Cabinet had become “abrasive” and “difficult”, his first acknowledgement of the growing split in the Tory Party.

However, eurosceptic ministers and MPs were left furious at the decision to send out the leaflet to every home in the country.

A number of senior Conservatives on Thursday asked Steve Baker, the eurosceptic MP running Conservatives for Britain, to approach Gavin Williamson, the Prime Minister’s Parliamentary aide, warning that they will oppose legislation if he does not withdraw the leaflet.

The Government has a working majority of 12, meaning that relatively few rebels would be needed to stop laws going through Parliament.

One MP said: “There is a huge amount of anger about this. So much so that there are discussions about organised rebellions to grind Government to a halt.”

Mr Baker said: “I think that Gavin has to know that they are furious and it risks real acrimony. There are some colleagues who have suggested we should vote against the Government's legislative programme.”

In a move that infuriated Downing Street, Mr Gove took to the airwaves on Thursday to denounce the Prime Minister’s decision to send out the leaflet.

"I want a fair campaign, I want people to hear from both sides,” he said. “What I think is wrong is spending £9million of taxpayer's money on one particular piece of one-sided propaganda.

"I think it is wrong that money that should be spent on priorities like the NHS is being spent on Euro-propaganda.”

Can you opt out of receiving the leaflet?

Under Royal Mail rules it is possible for a British household to opt out of receiving unaddressed mail being delivered to its door.

This would include anything from advertising offers to leaflets from central and local governments and public bodies – therefore including the new pro-EU mailshot.

However there are two reasons why this might not work very well for families hoping to immune themselves from pro-EU campaign material.

Firstly, it takes six weeks to activate the clause. Only once the opt-out form has been completed and returned would Royal Mail stop delivering. Given the 27 million leaflets are already being sent out they would likely be on door mats before the change came into effect.

Secondly, a household would have to opt out of receiving all unaddressed letters rather than just pieces of campaign material from the government.

That would mean leaflets explaining why Britain should leave the EU would not be received as well as more general targeted adverts which could be of benefit.