A leading Conservative backbencher has laid bare the extent of Tory frustrations with Theresa May by openly admitting he would not vote for the party if he wasn’t an MP, and had no interest in becoming a minister in a government he called “a shitshow”.

Johnny Mercer, who has represented Plymouth Moor View since 2015, said in an interview that in the current political situation there was “absolutely no chance” he would try to enter parliament, and intimated that May was an unimaginative “technocrat”.

Speaking to the House magazine – which last month ran an interview with Karen Bradley in which the new Northern Ireland secretary admitted knowing almost nothing about the region’s politics before she took the job – Mercer expressed deep disillusionment with modern Conservatism.

The former soldier was asked how the pre-politics version of himself would vote now. Mercer, who left the army in 2012, replied: “I wouldn’t go and vote. Just being honest, I wouldn’t vote. Of course I wouldn’t, no.”

Asked whether he would join the Conservatives, Mercer said: “If the situation was like it is now, I can safely say there would be absolutely no chance that I would try and be a member of parliament.”

Mercer, one of the more publicly prominent – and self-confident – members of the newer intake of Tory MPs, also indicated he had turned down a role in government and could never serve under May.

He said he was “asked to do a certain role and made it clear that I couldn’t for one reason or another”, adding: “I mean, would I want to be part of this administration? No.”

Mercer was blunter still about the current government, despite calling himself “inherently a team player”. “But when you go home from here on a Thursday and go for a run across Dartmoor or whatever, and you’re stripped to your core being, I mean, yeah, you realise it’s a shitshow,” he said.

The Brexit process had left the government and Tory party “in a position now where people are beginning to ridicule us”, said Mercer, who campaigned for remain in the EU referendum. He argued that the chaos could prompt voters to elect a Jeremy Corbyn government.

He told the magazine: “They’ll think, ‘Why should I vote for your government? Yeah all right, you might sort out Brexit eventually but actually, my operation was cancelled again last week. So, to be frank, I’m going to start looking elsewhere.’”

Mercer was scathing about the wider leadership of the Conservatives, and by implication May, saying too many senior party people were based in safe seats. Mercer took his constituency from Labour in 2015, initially with a majority of 1,000.

“The party will never really change until you have somebody who is leading the party who has won a seat and knows what it’s like to go out every weekend and advocate for what you just voted for that week,” he said.

He added: “We’ve lost focus on that for some very good, very capable but ultimately technocrats and managers. That’s not what Britain’s about.”

Mercer condemned May’s Chequers proposal for Brexit as “your classic professional politician’s answer”, which sought endless compromise and ended up pleasing no one.

Despite his many prescriptions for how the party and politics in general could work for the better, Mercer insisted he did not necessarily want to become prime minister.

He said: “My ambition here has always been to be defence secretary. I’d love to be a defence secretary who had 10 years to rip apart that department, make it work, get the offer right to our young people. We are such an amazing, proud military nation. It’s really tough to see what’s going on now.”