Downing Street has refused to reveal how many pro-EU leaflets were sent back in the post by angry voters.

The government caused considerable controversy in early April when it spent £9 million sending a leaflet to every household in the United Kingdom saying why it wanted Britain to stay in the European Union (EU).

Brexit campaigners accused the government of abusing its position and using taxpayer money to send out pro-EU “propaganda”, giving the ‘Remain’ campaign an unfair advantage.

A “Post It Back” campaign was soon launched to get people to send the leaflet back to 10 Downing Street, the Prime Minister’s official residence, at the expense of the government.

Some voters took to social media, saying that had defaced the leaflets with anti-EU slogans before sending them back.

AFP reported on voters such as Kirsty Stubbs, who wrote “What scaremongering rubbish” and “Vote Leave!” before sending it back, while Alex Armstrong took to Facebook to say: “Just sent back the propaganda leaflet to the freepost address with a suitably heavy attachment — a lump of concrete.”

Now, however, Downing Street has told Breitbart London that it does not have records on how many of the leaflets were returned.

A spokeswoman said that due to different types of postage it was impossible for the Prime Minister’s office to give an accurate number on the number of “return to senders” they received.

The Royal Mail also refused to comment on how many of the leaflets had been returned to sender.

The claim comes as polls move increasingly towards Brexit, with bookmakers now slashing the odds on Britain voting to leave.

Betting firm William Hill says that at the current rate, Leave will take the lead as the most likely outcome for this first time in the entire campaign this weekend. Graham Sharpe, the firm’s director of media relations, said the betting was now moving firmly towards Brexit.

“We were forced to shorten our Brexit odds yet again overnight,” he said “and having once been long-odds outsiders the odds have now come all the way down. The momentum is such that it seems inevitable Brexit will be favourite by the weekend if this trend continues.”