The shadow climate change minister, Mark Butler, has declared that after a federal election where Labor had its “backside handed to [it] by Fozzie Bear and Kermit the Frog – it’s time for some serious reflection”.

Butler, a senior Labor leftwinger and former federal party president, said on Monday the ALP should not attempt to sugarcoat the defeat in May, but instead ask itself hard questions.

“We just lost our third election in a row and the only majority we’ve won in the past 25 years was the majority of eight seats in 2007,” he said. “We got our lowest primary vote in a century, against a government the prime minister himself described as the Muppet Show.”

Butler used the opportunity of a book launch in Canberra to argue the current campaign review being spearheaded by Jay Weatherill and Craig Emerson “must be ruthless and unsparing” and include all policies, including in his portfolio area of climate change and energy.

He cautioned against reaching knee-jerk conclusions about the defeat, but insisted the campaign review needed to be “deeply uncomfortable” for all the protagonists if the ALP was to achieve the reset it needed and prepare itself for the contest in 2022.

“Nothing should be excluded or treated as sacrosanct,” Butler said. “The area I had responsibility for – climate change and energy – must be part of that thorough examination, as should all of our taxation policies and the spending commitments they were directed at funding.”

Butler said as Labor worked through the process of introspection about what went wrong with the 2019 pitch to voters, people needed to remember “how hard it is for Labor to win federally”.

He said Labor had become the natural party of government in state politics, focused as it is on the delivery of services, but said that “rightly or wrongly we face a much harder task when it comes to the bread and butter of federal politics: national security and broad economic management”.

Butler said the evidence about what was required for victory at the federal level was in. He said Labor’s three post-war victories “all involved an immensely popular leader, a compelling national vision and a superior campaign”.

He suggested there was an element of sleepwalking to defeat in May, with people putting too much store in polling showing that Labor was in front. “The truth is everyone thought this year we were cruising to victory on the back of a steady two-party preferred [result] of 52% or 53% and a primary in the mid to high 30s.”

Butler pointed out that Labor’s primary vote in federal contests, including 2007, when Kevin Rudd defeated John Howard, was well north of 40%. He also said that previous leaders who were unsuccessful in elections over the past 20 years, Kim Beazley and Mark Latham, presided when Labor’s primary vote was above 40%.

Butler’s line on how Labor needs to position itself going forward aligns with Anthony Albanese’s post-election declarations that the party needs a clean slate, but also needs to hasten slowly with formulating policies for the next federal election.

With the party review under way, and with senior figures positioning in advance of its conclusions, the current federal party president, Wayne Swan, has used a number of public outings in recent times to warn Labor not to throw the baby out with the bathwater in terms of the policy platform formulated under Bill Shorten’s leadership.

In a column for Guardian Australia in mid June, Swan cautioned colleagues not to overreact or attribute blame for the defeat “to any one person or policy”.

While Butler argues Labor was thumped in May by a suboptimal opponent, Swan has argued the election was “actually a close run thing” where primary vote swings were recorded against both the Coalition and Labor “although our poor showing in Western Australia and Queensland made victory almost impossible”.