The peer tasked with building a consensus on more powers for Scotland has told political parties to come to the table with proposals which meet the country's expectation for significant change.

Lord Smith of Kelvin said the next stage of devolution must be more than just "a list of apparently unrelated powers".

In a letter to the leaders of Scotland's five main political parties, he has urged them to take a ­"principles-led approach" to ­devolution, which draws from their existing published proposals for more powers but also takes account of the result of the independence referendum.

The SNP yesterday selected Scottish Government Finance Secretary John Swinney and Linda Fabiani MSP, a veteran of devolution discussions, to fight for extensive new powers for Scotland. Mr Swinney has said he intends to use former Labour prime minister Gordon Brown's ambition for home rule within a federal UK within two years as a benchmark for the Smith Commission's deliberations.

The Liberal Democrats, who appointed former Scottish secretary Michael Moore and former Scottish leader Tavish Scott to the commission, have similar ambition for federal home rule.

The Conservative Party, which has appointed academic Adam Tomkins and former Scottish leader Baroness Annabel Goldie, has said its desire to link Scottish devolution to further devolution for the English regions will not hamstring the Smith Commission's deal for Scotland.

The Scottish Greens will discuss their nominations at their party council, while Labour is also expected to reveal its representatives in the next few days.

The parties must submit their proposals to Lord Smith by October 10, and they will be published on the commission website shortly after.

A letter will also be sent out to Scotland's civic institutions inviting them to take part in the process, and Lord Smith will next week reveal how the public can share their views on additional powers with the commission.

In his letter, Lord Smith said: "In making your submission, I know all of the parties will be drawing on a substantial body of work, much of which has already been published.But I also know that everyone will want to reflect on their proposals in the context of the referendum campaign and outcome.

"These submissions will give us a starting point which will, I hope, end in a unifying set of recommendations agreed by all parties.

"The process by which we arrive at those recommendations will be vital."