With some justification, Labour has faced sustained criticism for its lack of substance on Scotland's constitutional question.

The Sunday Herald has persistently challenged Labour on this terrain.

For too long, the party's leadership has skirted around the issue with a position on devolution that barely takes Scotland beyond the existing settlement.

To an extent, some of this was to be expected given the party's decision to join a pro-union alliance with the Tories in 2014.

Until very recently, Scottish Labour leader Richard Leonard and UK Labour leader Jeremy Corbyn have shown scant regard for taking forward the debate on the constitution in the post-2014 era.

But in an interview with the Sunday Herald last month, Leonard said UK Labour should get a "move on" with its constitutional convention, aimed at examining plans for federalism.

While not endorsing Leonard's call, this newspaper felt it was a genuine attempt to kickstart a debate.

Now, UK Labour is responding with what appears to be a commitment of sorts to deliver a federal Britain.

Shadow cabinet office minister Jon Trickett’s backing for the “emergence through time of a federal Britain" is significant, given his brief of preparing Labour for government.

But with just under four years until the next election, voters in all parts of the UK have a right to know what Labour actually means by federalism.

The party cannot be left off the 'constitutional hook', or be allowed to let federalism become an ill-defined term as 'devo max' did some years ago.