Voters should bring along pens to EU referendum polling stations to avoid an MI5 plot, according to Leave campaigners.

Backers of Brexit are urging people to write in pen to ensure their ballot papers cannot be erased after the votes have been cast.

Leave campaigners say they are worried the EU referendum is being manipulated by the Government.

Two-thirds of Ukip voters believe there is a plot to rig the vote, while a third of them believe MI5 are involved in it, according to a poll this week.

Those warning about the conspiracy suggest MI5 or another government agency could rub out the crosses on their ballot papers before they are counted – presumably either spoiling their vote or changing it into a vote to remain in the EU.

Numerous people are sharing messages telling people to bring along pens to stop a possible conspiracy to rig the vote. Some have even taken to reminding people at polling stations, with people writing “USE A PEN TO VOTE” on polling station signs as a reminder.

Others have suggested that people should press extra hard when drawing their cross to ensure that it is still visible even if it is erased.

Though pencils are provided within polling stations, there is no legal obligation to vote with them and using your own pen will mean ballot papers will still be counted.

Voting rules are relatively relaxed and mean that people can theoretically vote with a tick rather than a cross if they wanted to.

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The Electoral Commission has welcomed people bringing a pen and said observers watch counts to ensure that they are kept secure. Campaigners from both sides have been invited to proceedings to ensure they are not being tampered with.

“By tradition, pencils are available in polling booths for voters to mark their ballot papers,” a spokesperson said. “If a voter wishes to bring their own pen and use that, it's fine.”

“In regards to security, at the count there are statutory observers to make sure that they are carried out correctly. Campaigners are also invited to observe the counts taking place.”

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