PLANS to give Holyrood the power to lower the voting age in Scottish elections have been criticised by peers who have complained that the move would lead to demands to extend the vote to 16 and 17-year-olds in other parts of the UK.

The Westminster Government has said it will fast-track the power to extend the voting franchise to Holyrood in time for Scottish Parliamentary elections next year, after the move to give the age-group the chance to participate in the independence referendum was hailed as a success.

However, members of the House of Lords Select Committee on the Constitution, chaired by former Tory Scottish Secretary Lord Lang of Monkton, have said it has been impossible for the UK Parliament to effectively scrutinise the proposed rule change, which it argues could have significant implications across Britain.

It raises the unlikely prospect of unelected peers throwing out the secondary legislation which would transfer power over the voting age to Holyrood by amending the 1998 Scotland Act.

Lord Lang said: "Changes to the law which impact on the UK Constitution, as the proposal to give the Scottish Parliament the power to amend the voting age clearly does, should be subject to full and proper Parliamentary scrutiny - not implemented by an unamendable statutory instrument.

"The proposed change will have knock-on effects across the rest of the UK and we are concerned that not enough thought has been given to this impact."

A report from Lord Lang's committee, released today, claims that if Holyrood passes legislation to lower the voting age it "may lead to pressure for similar changes to the franchise in the other devolved territories" and that "a voting age of 16 remains very uncommon around the world, and is not a change which any of the UK's main European neighbours has adopted."

The committee goes on to raise concern that the proposals to allow Holyrood the power to offer 16 and 17-year-olds the vote in local government elections, as well as Scottish Parliament polls, goes beyond what was recommended by the Smith Commission.

It adds: "The use of secondary legislation makes it impossible for Parliament to scrutinise this proposal effectively. This is not an appropriate way to proceed with significant constitutional change."

The report also raises concern over the data protection implications of allowing details of 16 and 17-year-olds on to the electoral register. It points out that when the voting age was lowered from 21 to 18 in the 1960s, the proposals were examined in far greater detail while in Ireland, a constitutional convention discussed the issue in 2013 and a referendum is to be held on whether 16-year-olds should be given the vote.

While the House of Lords have previously thrown out secondary legislation, most notably plans to open a super casino in 2007, the devolution of powers over the voting age has cross-party support meaning it is likely to be backed in a crunch vote on Thursday. All five Holyrood parties support allowing 16 and 17-year-olds the vote.

The SNP, which favours scrapping the House of Lords, said peers had provided further evidence of the "democratic absurdity" of the centuries-old institution.

Backbench MSP Christina McKelvie said: "The fact a Tory former Scottish Secretary and a group of unelected peers want to put roadblocks in the way of Scotland's young adults being given the vote speaks volumes - it is utter hypocrisy and shows how out of touch Lord Lang and his House of Lords colleagues are.

"These unelected peers believe that giving young adults the vote in Scotland will 'lead to pressure' for it to be extended to 16 and 17 year-olds in other parts of the UK - they are quite right, but that is something to be welcomed, not condemned.

"The bottom line is that Westminster must transfer the powers needed for younger people to vote in next year's Scottish Parliament election - regardless of what the House of Lords thinks. The referendum showed it can be done, in a way that doesn't create data protection issues, and Scotland's 16 and 17 year-olds must be given the chance to vote at Holyrood in 2016."