With the Tory-supporting media rounding on 'Red Ed', party comms chiefs Andy Coulson and Steve Hilton have identified a number of complementary attack lines.
In the run-up to David Cameron's speech at the party's annual conference in Birmingham, ministers indicated that the Tories would prioritise two themes - 'deficit denial' and 'union influence'. A third theme - 'yesterday's man' - was also inserted into Cameron's speech.
Tory strategists believe that if Miliband is seen to be against every major spending cut, there could be a short-term boost for Labour, but severe brand damage over time.
Miliband has previously insisted he will not oppose every cut the coalition proposes - yet the Tories are keen to disguise this message. Speaking on Monday, Chancellor George Osborne characterised Miliband's stance as: 'Let's delay the tough decisions. Let's borrow more. Let's go on adding to our debt.'
As the 'deficit denier' charge was hammered home by ministers at fringe meetings, top Tories also sought to stress the significant role the trade unions played in Miliband's election.
The Labour leader last week warned the unions he would have 'no truck with overblown rhetoric about waves of irresponsible strikes'. But in her speech, Tory chairwoman Sayeeda Warsi suggested that Miliband would 'follow Ed Balls and his union buddies and abandon the centre ground'.
The theme was also taken up by Education Secretary Michael Gove, who told a Guardian fringe event: 'Labour has a leader ... who owes his election to the trade unions. Ed finds himself in a position of power because of what the (union) brothers wanted to see happening in what they consider to be their party.'
At a Times/Populus fringe meeting, Health Secretary Andrew Lansley also questioned whether Miliband would stand up to the unions. However, in the same event, Populus MD Andrew Cooper warned the Tories against negative campaigning.
The pollster said: 'It may well be the case that Ed Miliband will come quickly to be seen as a catastrophic choice for Labour leader: it is too early to tell, though the early polling is not encouraging for him. But Gordon Brown was also, unarguably, a catastrophic choice for Labour leader and that fact alone was not sufficient for the Conservatives to win a majority at the general election.
'The Conservatives will be judged at the next election by what they have done in government and how well they have explained it. They should spend all their time focusing on that and none of their time thinking about how to characterise Ed Miliband.'
In his speech to the party faithful, Cameron duly refrained from naming Miliband. But in a swipe at the new Labour leader, Cameron said the Labour conference had been 'less Red Ed than redhead' – a reference to the former leader Neil Kinnock's prominent role at the Labour conference in Manchester last week.
Tory strategists suggested this was part of a wider plan to depict the new Labour leader as 'yesterday's man', with the message reinforced via giant posters in the the press office in Birmingham.
From Tuesday, media were treated to a giant poster of Miliband next to Gordon Brown, and another picturing Miliband alongside Tony Blair. A Tory source told PRWeek: 'Miliband has tried to free himself from the Brown and Blair years by talking about the "new generation". Our job is to make sure people don't buy it. What we're saying clearly is that he's yesterday's man.'
Speaking after Cameron's speech, Universities Minister David Willets explained why the Tory leader held back from heavy criticism of Miliband.
'Tribal politics and bashing other parties - people have a very limited taste for that,' he said. 'David Cameron as the Prime Minister is above getting bogged down in arguments about Labour. What he's trying to do is say "this is the direction in which this coalition government wishes to take the country"... And that argument doesn't need to be confused and complicated by scoring cheap points about Labour.'
How should the Tories deal with Labour's new leader?
Tim Collins, director, Bell Pottinger Public Affairs
The Conservatives need to be careful in their glee over Ed Miliband's victory. He is not Michael Foot, obviously unelectable from the first moment. So they cannot afford simply to write him off. But he is vulnerable. He won because he chose to be closer to the mainstream of his party than to the instincts of the country. Tories are right to say he represents not Labour's future but its pre-1994 past.
The Conservatives were terrified of Tony Blair, with reason. The only Labour leader to get more than 40 per cent of the vote in the past 44 years was seen by many, both supporters and opponents, as being more Tory than the Tories.
That is why the Red Ed tag hurts - because while the new leader is not a crypto-Communist, he is clearly not a closet Conservative either.
Britain has never elected Labour when its leader is on the left of his party. So the Conservatives should concentrate on the facts of Miliband's left-wing policies and beliefs. Those are what will defeat him - not a nickname.
Malcolm Gooderham, managing director, TLG
The Tories are trying to define Ed Miliband before he has a chance to do so himself. There are a range of options, but casting him as 'Red Ed' is ambitious at best. He is unlikely to be 'Red' in a way voters will relate to and recognise. And he will probably delight in showing voters why he is anything but - thereby repositioning himself, and looking and sounding like a moderate.
Such repositioning would carry two implications: first, it would make the Tories look out of touch and old-fashioned; second, it would allow Ed to appear to be on a journey and moving to the middle.
A modern Conservative strategy would challenge Ed to join the new values-based consensus epitomised by the coalition and to support the new agenda for Britain. Tories could then cast any hostility and negativity from the Labour leader as being dogmatic and playing politics on matters of national interest - an approach that 'tanks' with voters. Equally damning, his opposition would suggest that the new leader has similar instincts to his old boss Gordon Brown.
48.6 - Public's rating of David Cameron
43.8 - Public's rating of Nick Clegg
39.2 - Public's rating of Ed Miliband
35.6 - Public's rating of Tony Blair
Source: Populus polling of 1,508 adults by telephone in September 2010. Interviewees were asked to rate politicians on a scale of 0-100, with 0 indicating a negative view and 100 indicating a positive view