Lord Rothermere, the aristocratic proprietor of the Daily Mail, says the newspaper is "getting out of date" and may have to change its political colours from deepest blue to Blairite pink.
The latest recruit to Mr Blair's side sent shock waves through the Daily Mail editorial floors by suggesting that he believed the newspaper may have to change its political allegiance.
The day after it was disclosed he had crossed the floor of the Lords to the independent benches in broad support of Labour, Lord Rothermere hinted in an interview on BBC radio that the writing may also be on the wall for his "brilliant" editor, Paul Dacre.
Before polling day the Daily Mail warned its readers that 1,000 years of history might be wiped out if Labour won the election.
Lord Rothermere said he and the newspaper's editor "don't agree on many things".
"He is a great editor and therefore he is entitled to his views in the paper. I don't happen to agree with all of them."
Asked if Mr Dacre would be free to pursue his Euro-sceptic line in the Daily Mail, Lord Rothermere said it was a "free country" and Mr Dacre was "entitled to his views and to express them, but of course if they start to affect the circulation that will be different".
But asked whether the Daily Mail would have to change its views, he went on: "If they feel this is the new mood of our readers, yes they will - and I think it is personally.
"Paul has different views. Its readers don't take much notice of politics but in this case they may, and they may feel that the Mail is getting out of date."
Lord Rothermere wanted Mr Dacre to remain at the helm but also raised the possibility of his editor's departure. "I would be very sad to lose him. He is probably the most brilliant editor in Fleet Street."
Lord Rothermere, interviewed from a car travelling on the ring road around Paris, was also prepared to support Mr Blair over the abolition of hereditary peers in the Lords.
"That would not worry me at all. I am a democrat. I believe in democracy and the world moves forward ... Nobody has got an hereditary right to govern. I don't believe that at all.
"[Labour] are carrying out measures which the Tories should have carried out, helping small businesses, taking more adroit attitude in Europe." Colin BrownReuse content