A lack of decommissioning and proposed changes to the RUC have done "massive damage" to confidence in the peace process, senior unionists said last night.
The UUP review group was set up at May's meeting of the party's ruling Ulster Unionist Council when Mr Trimble narrowly secured permission to re-enter government with Sinn Fein. It comprises grass roots members from both the pro- and anti-agreement wings of the party.
The group was to monitor progress on IRA decommissioning and has the power to recall a meeting of the 860-member UUC to make a fresh assessment of their involvement at Stormont.
After meeting the International Commission on Decommissioning yesterday, the group issued a statement in advance of its full report, expected in a few days.
"We are deeply unhappy at the lack of progress on decommissioning which is essential to the full implementation of the Belfast Agreement. The Ahtisaari/ Ramaphosa inspection is a standalone attempt at confidence building. Actual, credible and verifiable decommissioning - the destruction of weapons - is the real measure of progress.
"Not only have republican and loyalist terrorists failed to decommission weapons, they have not even indicated if and when decommissioning might begin.
"The proposed changes to the RUC, outside the terms of the Belfast Agreement, and the lack of decommissioning had done massive damage to confidence in the process.
"Conference announcements by the Secretary of State of task forces [to combat paramilitary crime] do not measure up to decommissioning and the need for total support of the RUC. The government must act now to restore balance."
Meanwhile, the UUP's security spokesman, Mr Ken Maginnis, said he believed the IRA would soon allow another inspection of its arms dumps.
Speaking shortly before the group issued its statement, Mr Maginnis said "the Commission [on Decommissioning] knows exactly what we require".
The issue would not go away, he said, adding that the party was "determined to take steps to ensure that progress is made".
The new MP for South Antrim, the Rev William McCrea, condemned Mr Trimble's talks with Mr Ahern in Dublin.
He expressed amazement that Mr Trimble appeared to be asking the Irish Government to give him some "crumb of comfort" on the issue of the RUC.