There are still too many Scottish MPs at Westminster, a constitutional expert has told a committee of MPs.
The Scottish Parliament has thrown up constitutional questions
The number of Scottish MPs was cut from 72 to 59 after Scotland was given its own Parliament in 1999.
But Prof John Curtice, of Strathclyde University, said that number was still too high and could increase again under boundary changes.
"Scotland is, in fact, still over-represented in this House," Prof Curtice told the Justice Committee.
At the 2005 general election, the average number of people living in Scottish constituencies was about 65,000, compared with about 70,000 in English constituencies, Prof Curtice told the committee.
But because of boundary changes and England's population growing more rapidly, "the constituencies in Scotland are gradually getting smaller relative to those in England".
The number of Scottish constituencies at the next general election would be calculated by dividing Scotland's population by 59, rather than by comparison to England.
"Given the way in which the Scottish boundary commission is now interpreting the rules for redistribution, actually you can probably anticipate that the number of Scottish MPs will increase over the course of the next few redistributions and therefore the gap will re-emerge," said Prof Curtice.
"The Scotland Act failed to say that the quota in Scotland should be the same as that in England at each and every redistribution."
He said the boundary changes should instead be drawn to ensure "you at least catch up" with the aim of eventually reaching "equality".
Robert Hazell, professor of government and the constitution at University College, London, blamed the UK's "first-past-the-post" voting system for the "very heavy over-representation of Labour in Scotland and Wales, in terms of seats to votes".
He said one answer would be a "more proportional" voting system at Westminster or - giving the dominance of Labour in Scotland and Wales - an attempt "try and revive the fortunes of the Conservative Party" in those countries.
Cash currently being pumped into marginal seats in England by Tory donor Lord Ashcroft, should be directed north of the border, he suggested.
"Lord Ashcroft's fund should be increased and it should be specially directed towards Scotland and Wales and it should be called the West Lothian fund".
The "closest to a complete answer" would be a separate English Parliament but no "heavyweight" politicians had come out in support of such a move and there was "no significant public demand for that," he told MPs on Tuesday.
"English votes for English laws" at Westminster - the Conservatives' preferred solution - seemed "logical and fair".
But he warned that there could be "huge technical difficulties in identifying what counted as an English law" and the Commons Speaker, whose job it would be to decide, could be drawn into political controversy.
"I am in no doubt that over time what was introduced as seemingly a modest procedural change, could lead to a Parliament within a Parliament.
"And no one should be in any doubt that this would be a very big change indeed, with potentially very grave long-term consequences."
Another solution was handing powers to elected regional assemblies, said Prof Hazell, which although "dead for the time being" after being overwhelmingly rejected by voters in the North-East, should not be "written-off forever".
There was a similar message from Professor Charlie Jefferey, an advisor to then deputy prime minister John Prescott in the run up to the 2004 referendum in the North-East of England.
Voters had rejected the idea because they failed to identify with the "regional unit put before them" and because ministers refused to give up "significant powers" to the proposed new body, Professor Jefferey told MPs.
But many of the problems identified at the time - such as lack of a regional political voice in Westminster and economic "marginalisation" - still remained, he added.