Tory bosses have delayed sending out ballot papers in the party’s leadership contest amid fears cyber hackers could change people’s votes.
Under the initial rules of the race, party members would have been able to change their votes after submitting them if they decided to switch their support.
But that has been ditched after advice from the National Cyber Security Centre (NCSC), which is part of GCHQ.
The ballots had been due to be sent out from Monday but could now arrive as late as Thursday.
An NCSC spokesperson said: “Defending UK democratic and electoral processes is a priority for the NCSC and we work closely with all parliamentary political parties, local authorities and MPs to provide cyber security guidance and support.
“As you would expect from the UK’s national cyber security authority we provided advice to the Conservative Party on security considerations for online leadership voting.”
A Conservative Party spokesperson said: “We have consulted with the NCSC throughout this process and have decided to enhance security around the ballot process.
“Eligible members will start receiving ballot packs this week.”
The hacking concerns emerged as a new poll revealed that Liz Truss has increased her lead over Rishi Sunak in the leadership race.
The YouGov poll for The Times newspaper showed 60% support for the foreign secretary versus 26% for Sunak, with the remainder undecided.
It means her lead has increased to 34 points - 10 points more than YouGov’s last poll a week ago.
The poll was conducted before Truss was yesterday forced into a screeching U-turn on controversial plans to pay public sector workers in poorer parts of the country less money.
That followed a furious backlash from senior Tories, including Tees Valley mayor Ben Houchen.
He said the proposed pay policy had left him “speechless”, and suggested it would have cost the party the next general election if implemented.
Houchen told BBC Radio 4’s World At One programme that the “horrifically bad” policy “could be Liz’s dementia tax moment”, in a comparison to Theresa May’s scrapped policy that was blamed for her poor electoral performance in 2017