It is claimed a lower age limit may improve turnout

A growing number of organisations support a change, including the Scottish Parliament's local government committee.

It has been suggested the measure could at first be adopted for council elections.

The Electoral Reform Society's campaign group Votes at 16 said it could even improve turnout.

Turnout

In Germany, 16-year-olds can vote in many municipal elections.

And the authorities there have found that 16 and 17-year-olds are actually more likely to vote than the 18 to 35 age group.

Meanwhile, the conference is expected to hear heavy criticism of the government over the conflict in Iraq.

Speaking during a briefing in Inverness, STUC leader Bill Speirs said: "Obviously I can't pre-empt what the Iraq debate will decide and what we will come up with.

We have been invading another country without a UN mandate and in fact seriously undermining the UN Bill Speirs

"But I would be very surprised if we didn't adopt a position that was very critical of the decision by the UK and the US governments to invade Iraq.

"We have been invading another country without a UN mandate and in fact seriously undermining the UN."

Labour leader Jack McConnell is due to address the congress and Mr Speirs said he expected him to "reflect on the positives and the negatives" of devolution.

A total of 398 delegates were due to attend the congress, representing 46 trades unions and 32 trades union councils.