Rishi Sunak has narrowed the gap with Liz Truss in the Conservative party leadership race, with the foreign secretary leading by only five points in the latest poll of members.

The former chancellor’s campaign team have stressed in recent days that they were finding a much tighter race on the ground than polling suggested a fortnight ago.

The latest poll was conducted by Techne for a private client but data tables have been released for the poll of 807 Conservative members. However, separate polling by YouGov for the Times on Tuesday, although taken before Truss’s U-turn on civil service pay, had the foreign secretary with a huge 34-point lead, and 60% of the membership saying they would vote for her.

It comes after days of renewed momentum for Truss with a string of high-profile endorsements including Penny Mordaunt – a sign that ambitious ministers saw the race as sewn up.

Mordaunt, who was beaten by Truss to be Sunak’s challenger in the final stage of the leadership contest, said Truss was “the hope candidate”.

The endorsement came as a blow to Sunak after a bitter campaign during which supporters of Mordaunt blamed Truss for a damaging “blue-on-blue dogfight”.

Mordaunt was the latest in a number of new backers for Truss including the former leadership candidates Nadhim Zahawi and Tom Tugendhat, as well as the ex-cabinet minister Brandon Lewis and the West Midlands mayor, Andy Street.

The latest poll also includes significant positive numbers for Truss, suggesting her tax policies are far more popular than Sunak’s – though it was conducted before his announcement of further tax cuts over the next parliament. She was rated highly by 62% of members compared with Sunak’s 30%. But Sunak maintained an edge over Truss on Brexit, trusted by 50% versus 41%.

The polling expert Sir John Curtice said on Tuesday he did not believe the race was over. “We have to bear in mind that since Tory MPs decided that this was the contest between Rishi Sunak and Liz Truss, we have had one, I repeat one, opinion poll of the people who will actually have a vote, that is Conservative members. But that poll is now nearly a fortnight old,” he told GB News.

Another poll in the Sunday Telegraph of Conservative councillors also suggested the race was tightening, with Truss on 31%, Sunak 29%, and more than 30% saying they did not know.