Among voters in general in the Techne poll Ms Truss also has a significant lead with 40 points (up 5) to Mr Sunak’s 29 (down 4).
Techne chief executive Michela Morizzo put the massive increase in support for Ms Truss down to high level endorsements including surprise names like former leadership candidates Penny Mordaunt and Sajid Javid.
Mr Javid is a close friend of Mr Sunak’s and had been described by the former Chancellor as his mentor, but came out for the tax cutting Foreign Secretary instead.
Earlier in the contest there had been bitterness between the Truss and Mordaunt teams over briefings against the trade minister, especially on trans issues.
Additionally, high level supporters of Ms Truss such as Lord Frost came out questioning Ms Mordaunt’s professionalism and work ethic.
But in a shock move revealed by the Daily Express, Ms Mordaunt emerged at the Exeter hustings to argue that Ms Truss has the right vision for the country and is “the hope leadership candidate.”
Ms Morizzo also argued the Foreign Secretary’s policy platform, particularly tax cuts, was proving to be very popular among Conservatives and more widely.
The contest has been dominated by tax with Ms Truss promising to reverse Mr Sunak’s increases including the hike in National Insurance to pay for care.
While Ms Truss said she wants to encourage growth and keep the party’s manifesto promises not to increase tax, Mr Sunak claimed major tax cuts now are “immoral”.
Ms Morizzo said: “Our regular poll this week once again asked the question of Conservative party supporters: who do they favour more – Liz Truss or Rishi Sunak?
“Since our last poll Truss continues to grow her lead over Sunak and this increased support comes from a number of different quarters.
“Firstly, the almost daily and high-level MP endorsements continue to fuel support for the Truss leadership with the grass roots.
“These Party supporters are particularly satisfied with the policy focus Liz Truss has – cutting taxes, maximising work and growth, together with her clear and focused understanding of how the cost of living crisis is hurting people – particularly those families on lower incomes.”
READ MORE: Sunak drops huge inheritance tax hint with vow to ‘reward’ Britons
Significantly, Sunak trailed Starmer by 37 to 35, suggesting Truss is best placed to beat Labour.
Polling was carried out by Techne UK who surveyed 1,624 people on August 3 and 4.
Earlier this week private work they had carried out on 807 Conservative Party members was leaked and suggested Ms Truss had a 5 point lead over Mr Sunak.
But the recent polling suggests that the gap is now widening and a Yougov poll put Ms Truss and enormous 38 percent ahead of Mr Sunak among members.