The Conservative donor, one the party’s leading business supporters, said the Tories had “drifted out of touch” during the cost of living crisis and have shown an “inability to deliver”.
Mr Walker – who had once hoped to stand as a Tory candidate – declared that Britain was “in a considerably worse state” after 13 years of Conservative rule.
“It’s a really tough decision. I’ve always naturally assumed that Conservatives support business. What I was seeing coming out of the party was really conflicting with what I was seeing as a businessman,” the 43-year-old executive chairman told The Times.
The Iceland chief said he become uneasy about the idea of standing for the Tories because of “flip-flopping” on key policies and ministers’ “rhetoric” about immigration and climate change.
He said Mr Sunak’s decision to water down net zero targets – pushing back a ban on petrol and diesel car sales from 2030 to 2035 – was the “final straw”.
Mr Walker also condemned the prime minister for pretending to scrap “laws that didn’t exist, weren’t even proposed policy”.
The PM had highlighted a series of “worrying proposals” – including the possibility of a tax on meat and households being required to own seven bins – that he claimed he was axing. But government documents showed these ideas were never in government plans.
Mr Walker also condemned the idea of ditching HS2’s northern leg from Birmingham to Manchester. “UK plc needs stability and certainty and the issue is there’s just been so much flip-flopping,” he said. “Take HS2. I’m no fan of HS2 – but it’s better to do it than half do it.”
The Iceland boss has given just over £9,000 to the Tories. His father Malcolm, who founded the supermarket chain, gave £165,000.
Mr Walker rejected rumours that he was set to join Keir Starmer’s Labour party – but said he was “open to persuasion” on who to back at the next election.
It comes as leading Tory donor Philip Harris, founder of Carpetright, said Mr Sunak’s party did not “deserve” to win the 2024 general election.
A series of top Tory donors have denounced the party and pulled financial support, with some major backers even defecting to Labour as Sir Keir tries to “woo” big business.
John Caudwell, the Phones4U founder, said he will not back Mr Sunak after the “madness” of his U-turn on net zero pledges – and said he was thinking of giving to Labour instead.
Mohamed Amersi, who with his partner has donated £750,000 to the Tories, told The Independent earlier this month that he would give money to Labour politicians.
And Sir Rocco Forte – who gave £100,000 to the party to help fund the last general election – accused the party of reaping what it had sowed, claiming that “incompetence” had driven donors away.
Gareth Quarry, a former Conservative donor who defected to Labour, previously told The Independent that “dozens” of leading business figures – including Tory backers – had approached him asking how they could help to put Sir Keir Starmer in No 10.