Former Scottish first minister Jack McConnell and Peter Robinson attended the event
A row has broken out between Sinn Fein and the DUP after Peter Robinson said he wants to change the way the assembly makes decisions as soon as possible.
Mr Robinson said ending the veto that parties can exercise is as important as devolving policing and justice powers.
He was speaking at a conference in Belfast's Ulster Hall.
Martin McGuinness accused the first minister of returning from his Florida holiday suffering from sunstroke and spending "too much time at Disneyland".
It is understood the speech delivered by Mr Robinson was not the speech cleared by Mr McGuinness's office last week.
Instead of the three-page speech which underscored the achievements of devolution, Mr Robinson gave an address as DUP leader.
The first minister signalled there could be a delay in transferring policing and justice powers due to problems around finance.
He added there was no need to wait until 2015 to change voting rules and end community designation.
"The St Andrews Agreement provides for a review of arrangements by 2015 but we should address problems when they exist and not await an arbitrary date," he said.
Mr Robinson said: "It is not always going to be possible to reach an accommodation and as a result of our voting system a failure to agree means deadlock - this has been the case on a number of issues," he said.
Mr Robinson was speaking at a conference entitled "How can devolved government deliver for citizens", also attended by former Scottish first minister Jack McConnell.
However, Mr McGuinness said: "Peter's proposals appear to be some attempt to create the conditions where other parties can gang up on Sinn Fein, that will not be allowed to happen.
"The propositions expressed by the DUP leader are fantasy politics."
Mr Robinson told delegates that the abolition of community designation - the system by which assembly members are categorised as unionist, nationalist or other - was at the heart of proposals which his party will publish in greater detail later this month.
"As a consequence of this, new voting arrangements for the Assembly and the Executive will be required," he said.
"As a moral and practical matter, community designation is fundamentally flawed.
"It is deeply undemocratic, it entrenches community division and hinders the development of normal politics in Northern Ireland and in practice means that the votes of all Assembly members are not equal."
The Stormont voting system - created by the Good Friday Agreement - effectively hands those who control most unionist or most nationalist votes a veto over any initiative and was meant to act as a guarantee to either side.
Mr Robinson acknowledged this was an initial safeguard but said there were other ways to provide community confidence.
He said the DUP was proposing the introduction of weighted majority voting.
"Where a cross-community vote is required by legislation or triggered by a petition of concern, a proposal would require the support of 65% of Assembly members present and voting to pass," he said.
Mr Robinson said this would mean "that no single political party would have the capacity to block proposals which otherwise could command widespread support".
Mr Robinson reached out to the Ulster Unionists and SDLP, promising them more consultation ahead of Executive meetings.
He criticised the approach of these parties to date and the way they have handled Executive business, suggesting they had been "less than responsible" in their approach.
He said he would consider offering unanimity over decisions at the Executive table.
Mr Robinson is also seeking changes to the Ministerial Code which would require the first and deputy first minister within a "reasonable period" to table and permit a vote at the Executive on a matter proposed by any minister.
On the issue of policing and justice, he warned that the transfer of these powers could be delayed if the government maintains its present position on funding.
"The people of Northern Ireland would not thank us if we took on functions which are not properly funded and then be forced to divert funds from health and education to meet the shortfall," he said.
SDLP deputy leader Alasdair McDonnell said Mr Robinson's comments "regarding how he and his cohorts in Sinn Fein conduct Executive meetings demonstrate that our criticism has been entirely justified".
"In the wider community there is a steady growing sense of disappointment at the quality of devolved government with little policy innovation, poor prioritisation, no real decisions and no real delivery."
Ulster Unionist deputy leader Danny Kennedy questioned whether Mr Robinson's plans to give his party and the SDLP a greater role in Executive business was "an admission we haven't had the role we should have had".
He said the DUP's plan to abolish community designation "looks suspiciously like the DUP trying to change the rules because, having examined their performance in the Euro election, they fear that their vote will continue to collapse and that Sinn Fein will emerge as the largest party".