A former federal Liberal candidate who campaigned shoulder to shoulder with John Howard has spoken of a shift in political outlook and dismay with his old party that prompted him to join the Greens.

Neil Ennis, a lifetime Liberal voter who ran twice for the party, including in the seat of Brisbane in 1993, registered as a member of the Greens in February.

The small business owner represents a sizeable segment of the growing Greens base whose traditional allegiances lean right. The party, whose membership is said to have grown about 40% in the last two years, is aware of about 20% of their voters who give preferences to the Coalition over Labor regardless of what’s on their how-to-vote cards.

Ennis’s growing disillusionment with the Liberals in government was reflected in letters of concern to his federal member, Peter Dutton, in 2014.

He told Dutton that the government’s proposed changes to racial vilification laws and slashing the renewable energy target would prompt him to “actively campaign against” the party.

“I’m a long-time Liberal voter and small business operator but I am surprised at how many recent decisions by the federal government are alienating me,” Ennis wrote. “I feel like you guys are now hostile to most of the issues that are important to me.”

Kirsten Lovejoy, the Greens candidate for Brisbane, received a message of support out of the blue last month from Ennis, who revealed his own tilt in the same seat 23 years earlier for a party he was now “personally ashamed of” and which was “not worthy of the kinder, more compassionate Liberals who preceded them”.

Neil Ennis on the campaign trail with John Howard as the Liberal party candidate for Brisbane in 1993, visiting the Stubbies clothing factory in Newmarket. Photograph: Neil Ennis

Ennis wrote he was “ashamed of their homophobia, their inaction on climate change, their heartless treatment of refugees, their total capitulation to the big end of town, their cold-blooded attack on low-income working families [and] their ideological war on trade unions”.

“The party I joined 26 years ago was a lot more compassionate than the ideological Tories who are running it today,” Ennis wrote. “I’m so disappointed in Malcolm Turnbull. When he ousted Tony Abbott, I hoped that we might end up with a more compassionate, kind-hearted government.

“Instead we’ve got someone worse – a person who pretends to be a ‘small l’ liberal but is owned by the hard-right of his party.”

Asked by Guardian Australia if it was him or the party that changed, Ennis said: “I think both of us did. I totally admit that I’ve moved a lot more to the centre than when I was younger.

“When I was younger, I very much saw things in black and white. I thought, I run a small business, I don’t want to pay too much tax, I want to be left alone to do what I do well.”

Ennis said his experiences campaigning for the Liberals over two years were overwhelmingly positive.

This included being joined on the hustings by Howard, a party giant and wily campaigner who managed on a visit with Ennis to a Newmarket clothing factory to steer the pair away from a photo opportunity in front of sign reading “the Sweat Shop”.

“John Howard was great, really good to campaign with,” Ennis said. “He could smell an ambush a mile away.”

Ennis said his conversion to environmental causes came later.

“It was a really simple trigger for me,” he said. “Up until my mid-40s, I led a fairly sedentary life working in an office.

Neil Ennis, who has embraced the Greens after being a lifetime Liberal voter. Photograph: Liz Ennis

“Then I just decided to get fit and get outside and ride my mountain bike in the bush. Being exposed to the environment, I fell in love with it and I thought I want to do something to protect this.

“It might sound a bit new age but I feel like our country changed me – being out and seeing the landscape and seeing how important it was gave me an appreciation for it.”

Meanwhile, the Liberal party had “moved a lot more to the right and it saddens me to see it in the control of the conservative factions of the party”, Ennis said.

“The way they’ve treated asylum seekers, giving tax cuts to rich people in the hope the hope it trickles down. I think that’s an absolute lie and it’s shameful for them to push that policy.

“Their stance on gay marriage and that we’re going to have to go through this plebiscite to bring this into law in Australia, the way it seems so much harder for people on low incomes to get ahead.

“It saddens me and I wanted to do something about it. I figured the best thing I can do is get behind the Greens. I believe in what they’re doing environmentally, socially and economically. I think it’s responsible and it’s good politics.”