The new pan-Unionist coalition of opposition parties at Holyrood yesterday sought to make common cause with Westminster MPs in the constitutional debate. The talks at Holyrood were described variously as "a cup of tea about a cup of tea" and "the beginning of a long haul flight".

Labour, who might have been most nervous given they have a new leader-elect and prickly relations with Westminster colleagues, emerged fairly relaxed on those fronts.

The three opposition party representatives emerged from a meeting to discuss the powers of the parliament saying they were determined to bring their Westminster counterparts into the debate.

Sources close to the discussions, however, conceded it was slow going to find common cause - in particular with the Conservatives who have been implacable foes of Labour and and Liberal Democrats in the past.

Nicol Stephen, Liberal Democrat leader at Holyrood, Cathy Jamieson of Labour and David McLetchie for the Tories issued a joint statement.

It said: "Our three parties share the aim of building a strong and prosperous Scotland as part of a strong and prosperous United Kingdom.

"We reject independence. The real conversation, and the one in which the overwhelming majority of Scots wish to participate, is about how devolution can develop to best serve the people of Scotland."

The joint statement added: "Today's exploratory meeting was to start that process. Our initiative will not be confined to MSPs alone, any single parliament nor to any one part of the United Kingdom. It will be open to everyone who shares our desire to improve government in Scotland.

"The three parties have agreed to continue to work together on this issue, and will now hold discussions with party colleagues across the UK with a view to meeting again when parliament has reconvened."

The problem for the three parties is that any hint of a coalition will clash with their own supporters, while the collective call to action in terms of new powers for Holyrood plays easily into SNP hands.

An aide to First Minister Alex Salmond said last night: "These talks come in the wake of the Scottish government's National Conversation on Scotland's constitutional future, which is driving forward the entire process.

"By talking about developing the parliament, it's clear that the status quo is no longer supported by any party. We are delighted. The National Conversation train has left the station - it's a matter for the London-based parties which compartment they want to get on."