The Northern Ireland Secretary, Dr John Reid, claims he has no "certainty" that the UK will see a referendum on euro membership during a second term of the Blair government.
And he rejects suggestions that the attitude of the Chancellor, Mr Gordon Brown, toward a referendum could turn on his ambitions to succeed Mr Blair as prime minister.
In a wide-ranging interview about the general election for today's Irish Times, Dr Reid also insists he is not a unionist or "an advocate" for the union of Britain and Northern Ireland.
Asked if, like Mr Blair, he values the Union, Dr Reid says: "No. What I value higher in the context of Northern Ireland, as Secretary of State, is the right of the people in Northern Ireland to choose their own future."
Dr Reid's comments about the euro coincide with pressure on Mr William Hague to re double his attempts to make it a major election issue.
A raft of opinion polls yesterday gave Labour commanding leads of between 16 and 20 points, suggesting Mr Hague could be leading the Tories to an even bigger defeat than they experienced in 1997.
Despite being widely judged to have "won" the first week of the campaign, the bitter message from MORI's poll for the Sunday Telegraph was that the Tory leader's ratings remain lower than those of Mr John Major in 1997 or of Mr Neil Kinnock in 1992.
Even confirmed Conservative supporters appear unenthusiastic about Mr Hague's leadership. Four out of 10 of them apparently oppose his supposedly "populist" £8 billion tax-cutting, spending-cutting manifesto, while fewer than half of them (49 per cent) actually named his as the best candidate to be prime minister.
Moreover, while the Prime Minister and Chancellor remained under pressure over Labour's tax and spending plans, only 16 per cent said they regarded tax as a very important election issue.
The other good news for Mr Blair was that health and education topped the list of voters' concerns, as embarrassment threatened over crime and disorder and police numbers.
Labour claims to have identified at least 71 Conservative candidates who have defied Mr Hague by ruling out membership of the euro for ever in their personal election addresses.
In his interview Dr Reid answers "No" when asked if he is certain Britain will see a referendum on the euro during the lifetime of the next parliament. Asked if he thinks it conceivable that Gordon Brown's ambition to be prime minister could actually block a referendum, Dr Reid rejects "the premise" on which the question is based.
When asked if he means to question Mr Brown's desire to be prime minister, Dr Reid replies: "Yeah. Or that if he wanted he would take a given view on whether or not to have it [the referendum].
The Labour leadership successfully secured Tory defector Mr Shaun Woodward's selection yesterday as the candidate for the Labour seat of St Helen's South. But against a tide of local resentment it was a narrow affair, with Mr Woodward beating his nearest rival by just four votes after a count of second-preference votes.
Rory Bremner, the satirist famous for impersonating Mr Blair said yesterday he had been barred from joining the Prime Minister on the election trail because his caricatures are too close to the truth. Bremner was allowed to join the Tory Party on campaign stops.