A new group is calling for the Scottish Parliament to be given wide-ranging new powers regardless of the outcome of the independence referendum.

The group says it wants to secure a "stronger Scotland within the UK" by working towards full devolution of tax powers, giving Holyrood responsibility for raising all the money it spends.

Former Liberal Democrat MSP Jeremy Purvis, who is heading the Devo Plus group, said his proposals were more popular than independence or the current set-up.

The launch coincides with a survey which shows a growing number of people in England now support the idea of Scottish independence.

The latest NatCen Social Research British Social Attitudes Survey found 26% of English residents favoured ending the union - the highest figure yet in such a survey.

The study also uncovered signs of increased frustration about Scotland's position in the union, with 31% of people in England saying they "strongly agreed" that Scottish MPs should not be able to vote on English laws - up from just 18% 10 years ago.

The number of English people who feel Scotland gets more than its fair share of public spending has also been on the rise, with 44% now feeling this is the case, compared with 21% in 2000.

Both Prime Minister David Cameron and former Labour chancellor Alistair Darling have talked about an extension of powers for Scotland, while the SNP has not ruled out a "devo plus" option in the referendum.

At the launch of Devo Plus on Monday, Mr Purvis said: "The choice ahead of the people of Scotland is a clear one: whether to continue to be part of the United Kingdom or to leave it.

"Each political party, alongside trade unions, community and civic bodies will debate and discuss, but the people will ultimately make a choice. That choice can be an enriched one if it is not simply a contest between separation or the status quo.

"To secure a stronger Scotland within the UK we believe there can be a better way forward. We believe we have the basis of proposals which are not only better, but more popular than the status quo and independence."

He added: ""It is clear that a sizeable number of people in Scotland are not looking for independence or the status quo but for the best way of securing a stronger Scotland within the UK, for the long term. Devo Plus will offer precisely that.

"It is not a compromise solution. It is the best solution. It is the best way forward for Scotland regardless of the independence referendum."

Ben Thomson, chairman of Reform Scotland, added: "I have found it difficult to understand why the one option in this constitutional debate that seems to command most public support in the polls is not being championed by any significant organisation as the best solution both for Scotland as well for the rest of the United Kingdom."