David Cameron may be no closer to setting a date, let alone agreeing new terms of the UK’s status in the European Union, but in the background, the engines of the campaign machines are starting up.

Cameron outlined his shopping list of reforms at June’s summit in Brussels. They include cutting the phrase “ever-closer Union” from the treaty; protecting the UK from decisions by the euro club; and curbing welfare for EU nationals who move to Britain.

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Meanwhile, with his government’s referendum bill comfortably passing its second reading in the House of Commons, the political debate on the referendum will be quiet until the autumn.

But behind the scenes, the campaign machines are beginning to get to work.

The umbrella Yes campaign is in the process of putting itself together.

Labour’s most popular politician, Alan Johnson, a former postman turned cabinet minister and now celebrated memoir writer, will head the party’s Yes camp.

For the Liberal Democrats, the death of former leader Charles Kennedy has robbed them of one of their most popular and effective pro-European campaigners. Former cabinet minister Danny Alexander, whose pre-parliament career involved a stint as press officer for Britain in Europe, is a likely figurehead for their campaign.

On the Conservative side, Laura Sandys, a former MP for the South Thanet constituency in which Nigel Farage, the leader of the eurosceptic Ukip party, ran for election, will be one of the chief organisers of the party’s Yes bandwagon.

Office space has also been acquired by the UK-branch of the European Movement, an all-party pro-EU movement.

It will sit in Millbank tower, just a stone’s throw from the UK parliament, in a venue previously used as the headquarters of Labour and the Conservatives in their days in opposition.

On the eurosceptic side, more than 60 Conservative MPs have signed up to the Conservatives for Britain group, widely expected to become the focal point for the Tories’ No campaign.

A handful of Labour members have also registered the name Labour for Britain.

Purdah

One of the main disputes in the early debates on the referendum bill is whether the “purdah” should be respected.

The quaint term refers to a period of silence by ministers and civil servants during the final month of political campaigning in an election or other vote.

At the same time, the fledgling Yes campaign is in limbo.

The Labour and Liberal Democrat parties are currently leaderless - until September and mid-July, respectively - meaning that neither party can formally start the process of fundraising and hiring staff.

Besides, whatever Cameron secures from EU leaders cannot realistically be unpicked by opposition parties at home. The UK’s future membership will be based on Cameron’s terms.

While the Cameron government, let alone his Conservative party, is not certain what its recommendation will be, Labour has indicated that it will campaign for a Yes regardless of what results from the EU talks.

Senior Labour politicians have indicated that repealing possible opt-outs on social and employment rules, such as the directives on temporary workers and working time, would have to be dealt with after the next general election in 2020.

In other words, a future Labour government might simply sweep away much of a Cameron reform package.

For its part, Labour will back Cameron’s plan to allow a group of national parliaments to “red-card” draft legislation from the European Commission and for tighter control of migrant access to welfare benefits, even though it believes the latter objective can be achieved through changes to domestic rather than EU law.

Trade unions

“Labour is in a position of leadership on this because fundamentally we are in favour of EU membership,” a senior Labour politician told EUobserver, adding that the party will start making regular visits to Brussels and other European capitals in a bid to strengthen its position with sister parties and other EU leaders.

This sounds noble, but it could cause problems for the party’s relations with its trade union paymasters if Cameron manages to secure opt-outs from EU employment and social protection legislation.

Last week the GMB trade union, one of the largest donors to Labour, warned in a letter to EU leaders that it might be forced to campaign for a British exit “if the EU commission and member state governments allow Mr Cameron and his government to undermine employment and social rights and their application to British workers”.

Labour is also anxious not to repeat the tactical mistakes it made during the Scottish independence referendum.

The party found itself campaigning on the same ticket as a Conservative-led government, which is widely disliked in Scotland, and defending an imperfect status quo. Defending continued EU membership on Cameron’s terms risks tainting the party, even if Labour has stated that it will not share a campaign platform with the Conservatives.

Scotland 2.0

Despite losing the Scottish referendum, the Scottish National party was made immeasurably stronger by the campaign.

In the EU in/out vote, even if Britons decide to stay in by a 65-35 or 60-40 margin, Ukip - which is now Labour’s closest challenger in dozens of seats in its heartlands - could benefit in a similar fashion.

“The EU is a non-stop reform process”, says Richard Corbett, one of Labour’s most senior and pro-European MEPs. “The idea that you negotiate something in 2015, agree in 2016, and its all done with by 2017, is unrealistic”.

It is hard to disagree.

Whatever the outcome of Cameron’s negotiation phase, and the referendum, the UK’s EU status will dominate domestic politics for at least the next five years.