Warrington South MP David Mowat highlighted a "fundamental flaw" in the Government's deal to allow mid-teens to vote in the 2014 referendum on Scottish independence.
Under the deal between UK premier David Cameron and Nationalist first minister Alex Salmond the franchise will be extended to 16- and 17-year-olds in the one-off poll. But in the Commons Mr Mowat, a member of the Scottish affairs select committee, quizzed ministers on the Edinburgh Agreement, claiming that the deal was a "piecemeal" part of tense negotiations either side of the border.
He added: "What concerns me is that 16-year-olds will vote on the sovereignty of their country, but six months later they will be unable to vote in council elections. How can that be right or coherent?"
Scottish Under-Secretary David Mundell replied: "The Government do not support the extension of the franchise to 16 and 17-year-olds, and indeed our Conservative colleagues will argue against that proposal when it comes before the Scottish Parliament."
But he added: "It will be for the Scottish Government to make the case for 16 and 17-year-olds voting in the referendum. That debate needs now to go to Scotland, to the people of Scotland and parliamentarians in the Scottish Parliament, so that there can be a full and proper debate."
He said that he remains hopeful that the Edinburgh Parliament will fully scrutinise the proposals and, "if they are defective, reject them."
Speaking after the debate, Mr Mowat added:
"Allowing 16 and 17-year-olds to vote is a major change in electoral franchise, but here it seems to have become a bargaining chip in broader wrangling between Westminster and Holyrood over an independence referendum. That is a fundamentally flawed process."