The Tory press release has been made public courtesy of Kevin Maguire, who also reports the Sunday night Radio 5 similar quote - kudos to Kevin Maguire here. Read the full story there, but key elements of the press release are:

From: Jackson, Richard N. Sent: 17 February 2008 17:54 Subject: Osborne: The day Labour's reputation for economic competence died

Press Release Conservatives
...
KEY QUOTES

Alistair Darling and Gordon Brown on nationalisation of Northern Rock

Darling accepts Nationalisation as a disaster

Jim Cousins (Newcastle upon Tyne, Central) (Lab): Does my right hon. Friend accept that the policy of nationalisation would lead to a slow lingering death for the jobs of the Northern Rock workers, its assets and Britain's reputation as a major financial services centre, with my right hon. Friend the Chancellor cast in the role of undertaker-and that only by finding a successor business to grow on those jobs, assets and reputations can we offer any real prospect of the taxpayers getting their money back?

Mr. Darling: I agree with my hon. Friend. 19 Nov 2007 : Hansard Column 968

For reference the full quote from Hansard annotated Q1/A1 and Q2/A2 with my view on how the answers relate to the quote/question:

Jim Cousins: [Q1] The whole House will have noted that the Liberal Democrats have as much regard for the 5,500 employees of Northern Rock in the north-east—and the 6,500 nationally—as they had for the job of their former leader. [Interruption.] Two or three faces in public, 10 in private—that is the policy of the Liberal Democrats. [Q2] Does my right hon. Friend accept that the policy of nationalisation would lead to a slow lingering death for the jobs of the Northern Rock workers, its assets and Britain’s reputation as a major financial services centre, with my right hon. Friend the Chancellor cast in the role of undertaker—and that only by finding a successor business to grow on those jobs, assets and reputations can we offer any real prospect of the taxpayers getting their money back?

Speaker: Order. I remind Members that they must ask brief supplementary questions.

Darling: [A1] I agree with my hon. Friend. It is regrettable and surprising that the Liberal Democrats never seemed to support our earlier proposals to keep Northern Rock open. [A2] It would also, however, be a mistake to shut off all other options and simply go for one at this stage; that does not seem to me to make any sense at all.

The BBC alleged A1 is in answer to Q2, but Darling intended that A1 as agreement with Q1 only. His A2 is in answer to Q2, not what the BBC suggested.

Nick Robinson should have seen this straight away had he studied the full Hansard quote - which turned out to not properly represent what Darling said as well.