Senedd members debated the Labour Welsh Government's record over the past four years, with the next election looming in 12 months.
Rhun ap Iorwerth accused Labour of failing to stand up for Wales and live up to promises made at the start of this Senedd term.
The Plaid Cymru leader told the Senedd: "Everywhere you look – whether it's the NHS, our economy, schools or society more broadly – the situation is worse now."
The would-be First Minister pointed to long NHS waiting lists, a "stagnant" economy, child poverty rates and "deteriorating" education standards.
But others accused Plaid Cymru of "gesture politics" after "propping up" the Labour Welsh Government for most of the past four years.
'Slaughter'
Leading the debate on a Plaid Cymru motion on Wednesday, exactly one year before the next election, Mr ap Iorwerth directed his ire at the "disgraceful" legacy left by the Tories.
He said: "It's no wonder they suffered a slaughter electorally in Wales last summer and the opinion polls for the Senedd election suggest they are increasingly irrelevant."
"But the excuses are far harder to bear now the Labour Party is in government in Westminster, something that was pledged time and time again by Labour members for years prior to the election would lead to change for the better."
The former BBC Wales journalist criticised UK Government decisions to slash the welfare budget and restrict winter fuel allowance – "cuts even George Osborne would wince about".
Mr ap Iorwerth accused the Welsh Government of spending all its energy over the past year managing "internal chaos", including three first ministers and "reshuffles galore".
'Embarassing'
Paul Davies argued Plaid Cymru should be held accountable for the Welsh Government's record due to the now-collapsed cooperation agreement between the two.
The Conservative said: "Plaid Cymru has been instrumental in propping up the Welsh Government and voting through its policies...they've done it on and off for years.
The deputy leader of the opposition added: "Plaid should be embarrassed they're calling for more powers. They haven't been able to help Labour use the powers they currently have."
Mr Davies warned Wales has "languished" at the bottom of league tables for years whether it's NHS performance, educational standards or economic activity.
He accused Welsh ministers of "doing nothing" in response to UK Government changes to inheritance tax for family farms and winter fuel allowance.
'Crocodile tears'
Jane Dodds, Welsh Liberal Democrat leader and the party's sole Senedd member, also pointed out that Plaid Cymru had a seat at the table as part of the three-year budget deal.
She said: "You've helped to steer the ship and you don't get to act surprised about the destination when you have actually been holding the map."
Ms Dodds, who struck a £100m deal with ministers to pass the latest Welsh budget, urged Plaid Cymru to take ownership of achievements such as free school meals.
The former social worker criticised the Conservatives' "shameful" amendment for failing to acknowledge the party's part in causing child poverty.
"Spare us the crocodile tears, please," she said. "To claim that a Conservative Welsh Government would do better for our communities is, frankly, insulting."
'Unwavering'
Labour's Julie James said the party has been forced to govern in the context of "deep austerity, mismanagement and short-termism" from a Conservative UK Government.
The minister told the Senedd that the Welsh Government has "stood unwavering" despite 14 years of the worst financial climate in the history of devolution.
Ms James raised examples including free prescriptions, universal free school meals in primaries and the education maintenance allowance for disadvantaged young people.
She pointed to "tangible progress" on health, with waiting lists falling three months in a row.
Criticising "posturing, gesture politics" from Plaid Cymru, Ms James said: "Wales deserves fair funding and this Labour government, led by Eluned Morgan, will keep demanding it until we get a settlement that reflects our needs and respects our nation."
Senedd members voted 35-11 against the Plaid Cymru motion. Conservative and Labour amendments also fell.
With the final vote deadlocked at 23-23, deputy speaker Dai Rees used his casting vote against the Welsh Government's amendment in line with convention.
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