By Nick Assinder BBC News Online political correspondent

As is so often the case, it is not what the prime minister says but the way he says it.

When pressed by Jeremy Paxman over his policy towards the single currency, Tony Blair made it crystal clear he favours entry in principle.

In or out of the euro

And his remarks came just hours before it was claimed that the government was planning legislation for a referendum in the next session of parliament, which starts in November.

And, no one watching his Newsnight performance on Wednesday will be in any doubt about where the prime minister's heart lies.

He wants Britain in and will be happy, possibly even delighted, to go down in history as the man who got the UK to change currency from the pound to the euro.

Click here to watch the interview

His enthusiasm for Europe shines through the interview as he insists it would be a betrayal of the national interest to stand aside purely for political decisions.

New momentum

Those opposed to euro entry, however, insist that it is the prime minister who is set to take a political decision in favour of the single currency.

They argue, with some justification, that the famous five tests are either so meaningless or subjective as to ensure the final decision on membership is a purely political one.

There is no doubt that there is currently a new momentum building over the euro.

The different wings of the Tory party, which have remained silent on the issue since the election of Iain Duncan Smith, have finally broken cover.

Former Chancellor Kenneth Clarke has unveiled a new, pro-European Conservative group declaring its voice must be heard.

Anti-Euro Labour members have launched their campaign headed by the likes of Harry Enfield and Vic Reeves.

Get on with it

At the same time 32 Labour backbenchers have signed a motion calling on Tony Blair to press ahead with a referendum on the issue.

Meanwhile, there is a growing row in parliament over the revelation that the Treasury select committee has abandoned plans to hold an inquiry into the five tests.

The committee's Labour chairman has been accused of doing Chancellor Gordon Brown's bidding by blocking the inquiry.

The suspicion is that this is to ensure there can be no chance of the committee challenging a positive decision from the chancellor.

All this amounts to the end of the self-imposed silences over the issue which now looks like dominating the coming year.

Yes vote

The prime minister is sticking to his pledge to examine the five tests by June of next year - and to then hold a referendum on membership of the euro.

The widely-held view is that he and Gordon Brown have now come to an agreement over the timetable for the referendum and that it may happen swiftly after the examination of the tests.

Depending on the ease with which legislation for a referendum is then pushed through parliament, it could be held before the next general election.

Some speculate it could even be held on the day of the election.

But if the prime minister wants to win a "yes" vote, he will have to mount a long campaign to win over sceptical voters.

It looks like that campaign is about to be engaged in earnest.

Watch the third and final part of Tony Blair's interview on Newsnight on Thursday on BBC2 at 2230 BST.