The Conservatives have promised to “end the assembly gravy train” if they win power at next May’s Senedd election.
At the Welsh Tory conference, party assembly group leader Paul Davies pledged to halve the number of Welsh ministers to seven.
He said he would freeze civil servant recruitment and not increase the budget of the body which runs the assembly
“We will not be abolishing the assembly, but we need to listen more” to those who want to, he said.
Prime Minister Boris Johnson will address the annual conference, in Llangollen, in the afternoon.
Welsh Conservatives are in good spirits after general election successes, but there have also been serious problems involving some of their politicians.
The party won six seats from Welsh Labour in December, giving it 14 MPs in Wales and its best result since 1983.
However in recent months AM Nick Ramsay challenged the Tory assembly group leader in court for suspending him from the group.
There have also been allegations over the previous business dealings of new Conservative Bridgend MP Jamie Wallis.
Monmouth AM Mr Ramsay was suspended from the party and the assembly group after being arrested on New Year’s Day but released without charge.
He returned to the group last month but remains suspended from the Conservative Party and has said he is considering further legal action over the matter.
But on Friday Mr Davies wanted members to turn their minds to next year’s Senedd election, hoping momentum from the general election will help end two decades of Welsh Labour rule.
Taking to the stage to the Queen song “Don’t Stop Me Now”, he told the conference “a Welsh Conservative Government will cut the cost of politics”.
“We will seek to freeze the Assembly Commission’s budget for the full five year term,” he said.
“There will be no increase in the number of politicians in Wales under my leadership.
“I will reshape the government too. I will reduce the size of the Welsh Government from 14 ministers to a magnificent seven.
“A 50% cent saving on day one.”
The party, he said, was “within a hair’s breadth of putting an end to Labour’s grip on power”.
In his speech, Mr Davies said that the 20th anniversary of devolution marked “20 years of failure” for many people.
He compared “elites” in Cardiff Bay to Brussels, saying many people felt remote from power.
But he said it was Labour, not devolution, that had failed and the Conservatives had consistently criticised the Welsh Government’s record on public services such as health and education.
The Labour Party, Mr Davies said, had wasted money on Cardiff Airport, a Pinewood film studio and the Circuit of Wales race track project.
He promised a Welsh Conservative government would upgrade the A55, build an M4 relief road and double investment in flood defences.
In a message to First Minister Mark Drakeford he added: “I’m telling you Mark, your time is up. I’m coming for you.”
Later, Welsh Secretary Simon Hart told party members their party was “an unstoppable force” after the general election victory, claiming Paul Davies had a “realistic chance” of becoming first minister in 2021.
On Welsh Labour, Mr Hart said: “For a government to be in office every year for 22 years cannot be healthy”.
The conference comes after a second coronavirus case was confirmed in Wales and those attending have been urged to help curb the spread of the disease by using Conservatives-branded hand sanitiser and following the official advice.
By BBC Wales political editor Felicity Evans
With some smaller parties now challenging the very existence of the Welsh Assembly, it looks like Paul Davies wants to head them off at the pass.
He’s hoping that promises to crack down on the cost of Welsh politics, while supporting the existence of the institution itself, will vacuum up a lot of centre-right votes in next year’s assembly election.
But is it a route to power? That’s much less certain.
His positioning here – the nod towards the devo-sceptics – will do nothing to endear him to Plaid Cymru, with whom he might need to work if he wants to push Labour out of power next year.