Scottish Liberal Democrat leader Nicol Stephen has said his party would oppose any UK Government move to take powers from Holyrood.
He criticised Gordon Brown's comments that the Holyrood-sanctioned commission on Scotland's constitutional future could be a "two-way street".
But Mr Stephen insisted he would not walk away from the commission.
His comments came in a BBC Scotland news webcast before his party's spring conference in Aviemore.
The three-day gathering is the first since the party lost power after last May's Scottish election.
The Liberal Democrats had served in coalition government with Labour since 1999.
Mr Stephen, who was answering questions from BBC Scotland news website users, insisted that the review group was not a "review" but a "commission", however the UK Labour government wanted to describe it.
The constitutional commission, voted for by MSPs, came after the Scottish Government launched its national conversation on Scottish independence.
During an interview with the BBC on Sunday, 17 February, Mr Brown said that the review was not a "one-way street" and some powers could be returned to Westminster.
Reacting to those comments, Mr Stephen said: "It's not something the Liberal Democrats are up for. We would oppose it."
He said the commission was the correct vehicle for devolving more powers to Holyrood, but added: "Where I would be critical is over the dragging of feet and the suggestion this could be about removing powers as well as giving new powers to the Scottish Parliament."
Nicol Stephen answered questions sent in by BBC website users
During the half-hour interview, Mr Stephen also refused to withdraw his remark that the Scottish Government's handling of Donald Trump's £1bn golf resort plan for Aberdeenshire "smelled of sleaze".
The project for the Menie Estate, called in by ministers after being rejected by the local council, will now be the subject of a public local inquiry.
The Scottish Parliament's local government committee, which also probed the affair, is expected to issue its findings shortly and Scotland's top civil servant.
Mr Stephen said: "There was enough concern for there to be a full committee inquiry through the Scottish Parliament and all the parties agreed that the inquiry should proceed."
The webcast, which was hosted by BBC Scotland political editor Brian Taylor, prompted more than 130 questions from users of BBC Scotland's news website.