David Cameron is running his EU negotiations on the basis that he effectively has a nine-month window from the summer of next year to the spring of 2017 to hold his in/out referendum on Britain’s EU membership.

As the main pro-EU group launched its campaign with warnings about the economic dangers of a UK exit, a new timetable emerged when the Europe minister, David Lidington, outlined a series of obstacles standing in the way of the vote.

Lidington told peers on the EU select committee that it would not be the “optimum solution” to hold the referendum after 1 July 2017 when Britain takes over the rotating presidency of the EU. François Hollande, the French president, is understood to have told David Cameron that he does not want the referendum to interfere with the French presidential election, which will be held over two rounds in April and May 2017.

As a result, ministers are working on the basis that the referendum should be held, in ideal circumstances, no later than the spring of 2017. Ministers are also assuming that they will be unlikely to be able to hold the referendum any earlier than June next year because of the need for a four-month period of grace once the act of parliament introducing the referendum has been introduced.

The details of the likely timing of the referendum emerged as one of the main figures in the pro-EU campaign warned that fugitives across Europe will flock to the UK as a safe haven if it leaves the European Union because a series of laws and extradition agreements would be ripped up. Sir Hugh Orde, the former head of the Association of Chief Police Officers (Acpo), said criminals would know that it would take longer to extradite them if Britain were outside the EU. He said: “If I was a villain somewhere else in Europe and I’m escaping justice, I am going to be here because it is going to take a lot longer to get me back.”

Orde was speaking at the launch of the pro-EU Britain Stronger in Europe campaign led by the former M&S executive chairman, Stuart Rose, who issued a strong warning of the economic impact of an exit. In an echo of the pro-euro Britain in Europe campaign launched in 1999, Lord Rose claimed that 3 million jobs would be put at risk if the UK quit the EU.

But Rose edited his speech to remove a claim, briefed overnight, that those who believed Britain should leave the EU were “quitters”. Will Straw, the executive director of the in campaign, said it stood by the description but Rose had edited his speech on Monday morning.

Rose is the main figurehead of the campaign. But Straw indicated the campaign hopes David Cameron would, following a successful renegotiation of the terms of Britain’s EU membership, be its main advocate.

Straw said: “Of course we’d love the prime minister and the government to campaign to stay in the EU because we hold a conviction that Britain is stronger, safer and better off in the EU. But obviously that is a matter for him and his government and where he ends up with his renegotiation.”

Boris Johnson, who has been courted by the two sides in the referendum campaign, raised the stakes when he suggested that Britain has little to fear outside the EU. Speaking during a visit to Japan, the London mayor said: “We want, in an ideal world, to stay in a reformed EU but I think the price of getting out is lower than it’s ever been. It’s better for us to stay in, but to stay in a reformed EU. That’s where I am.”

The prime minister is planning to outline his four-point plan to renegotiate terms of Britain’s EU membership at the end-of-year European summit in Brussels in mid-December. Cameron will call for Britain to be exempted from the EU’s historic commitment to create an ever-closer union of the peoples of Europe. This demand is being dubbed in Whitehall as the chapeau (hat) on his negotiations because it would allow Britain to claim that the UK opt-out from the single currency means that the EU is a multi-currency union.

The prime minister will also call for a group of national parliaments to be given a red card to join forces to block EU legislation. His final demand – a four-year ban on EU migrants claiming in-work benefits – is proving particularly troublesome, as Britain’s natural allies in eastern Europe indicate they are strongly opposed to the proposal which would, they believe, be targeted at their citizens.

Lidington made clear the four-year ban on in-work benefits still remains on the table after the Sunday Telegraph omitted it from a list of four demands being drawn up by Downing Street.

But Lidington indicated that Britain might have to bypass the European council – the body made up of all the EU’s 28 leaders plus the president of the European commission – to introduce changes to benefits. He said the best way may be to codify a series of judgments in the European Court of Justice which have suggested that member states have a greater than expected leeway over benefits.

Lidington made clear that the timing of the referendum will ultimately be decided by the pace of the negotiations. The prime minister acknowledges that the longer he takes to complete the negotiations the more time the anti-EU groups will have to muster their forces. He has been heard to joke in private that those who have campaigned hardest for a referendum for two decades – hardline Tory eurosceptics – are now the most keen to delay the vote. But the prime minister believes that it would be fatal to rush the negotiation and put a weak package of reforms to voters.