By Nick Assinder
Political correspondent, BBC News website
There is an odd symmetry to the fact that a fierce debate over Trident will rage during Tony Blair's final weeks as prime minister.
Labour opposed Trident in the early 1980s
The abandonment of old Labour's early 1980s unilateral disarmament policy was one of the highest profile steps along the long road towards the creation of New Labour, and the election win of 1997.
The embracing of Trident by Tony Blair succeeded, in New Labour's view, of putting behind them the election-losing policies of previous leaders, notably Michael Foot and his 1983 election manifesto - branded "the longest suicide note in history" by Labour's Gerald Kaufman.
The policy was retained in the 1987 manifesto and Neil Kinnock and his successor John Smith regularly witnessed their party conferences voting to keep it - moves that were ignored by the leadership.
But, since 1997 the issue has hardly featured in any election campaign and those left-wingers and CNDers who once led the debate - and which once included Mr Blair himself - have been pretty effectively marginalised within the Labour Party.
And there have been no serious attempts to return to the old policy - until now.
Thanks to coincidental timing - itself a matter of debate amongst MPs - one of Mr Blair's final acts as prime minister will be to commit Britain to renewing its independent nuclear deterrent.
The Vanguard-class nuclear powered submarines which carry the Trident missiles start coming to the end of the lives from 2019 and replacements take 14 years to design and build.
CND led the anti-nuclear debate
The US-made Trident II D5 missiles also need updating and it is expected that Britain will join a US Navy life extension programme which will enable them to remain in service until the 2040s.
Replacement of the submarines then is seen as necessary by around 2024 if the deterrent is to be maintained.
The Liberal Democrats and many Labour MPs believe that means there is no need for a decision now and claim Mr Blair is bowing to defence industry pressure and a desire to seal the decision before his departure.
Other opponents also claim that things have moved on since the 1980s, most notably the nature of the perceived threat which then came from a nuclear-armed Soviet Union.
Supporters of a replacement, however, point out that the world is now arguably less predictable with other states like Iran and North Korea developing nuclear weapons.
They also argue the retention of Trident keeps Britain at the top table in global diplomacy and within the UN.
There is also an argument over whether replacement breaks Britain's responsibilities under the international non-proliferation treaty - something fiercely denied by ministers.
Finally, there is also a debate over the fact that Britain's nuclear capability is so bound up with America's that it could easily manage without its own independent system and rely entirely on the US.
What many MPs want is a full, long, public debate over all these issues - something they complain the prime minister is determined not to give them.
There will be a debate in the Commons in the new year, but there will only be a take-it-or-leave it vote on the government's proposal.
And, even with possible concessions on the size of the deterrent held out by the prime minister in his Commons statement, that will not be enough to buy off all the opponents.
It may have come as a surprise to see one poll suggesting that, despite the apparent successes of New Labour, 39% of Labour MPs oppose replacement of Trident.
It will not see the prime minister defeated but may well once again see him relying on Tory votes to get his way.
That is something opposition leader David Cameron was eager to point out in the Commons, suggesting - as he did with the education bill earlier this year - that he was ready to support the right policies.
He will undoubtedly enjoy the fact, however, that that will only further irritate Labour rebels.
The upshot of next year's vote will be to spare Mr Blair's likely successor, and fellow Trident supporter, Gordon Brown, a divisive debate in his early days in No 10.
But it will also remind voters of that old Blairite catchphrase that: "We were elected as New Labour and we will govern as New Labour."