Media playback is unsupported on your device Media caption Gordon Brown replaced David Cameron at the event at the last minute, as Laura Kuenssberg reports

Labour voters have the "most to gain" if the UK stays in the EU, ex-PM Gordon Brown has said, as the party seeks to rally its supporters behind Remain.

Mr Brown said the UK could take a lead in the EU to create jobs, cut energy bills and tackle tax havens.

"We should be a leader in Europe, not leaving it," he said, as he set out what he called a "positive" case for a Remain vote on 23 June.

Vote Leave dismissed what it called a "hastily cobbled together re-launch".

And Boris Johnson, one of its leading campaigners, said the Remain side was "rattled" with just 10 days to go until the referendum on the UK's future in the EU.

In other campaign developments:

The Remain campaign believes Labour voters are crucial to winning the referendum, but it is concerned that many may not turn out to vote - or may support Brexit.

In a speech in Leicester, Mr Brown - whose late intervention in the Scottish independence referendum was considered an influential factor by some observers - sought to galvanise Labour support for the EU.

He said action on the environment, cutting energy bills, enhancing workers' rights and social standards, and tackling tax havens were all best achieved by being inside the EU.

And he argued the challenges of globalisation meant greater co-operation between countries was needed.

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"That is going to be the lesson we have got to learn from this debate in this referendum - that the EU is not the cause of the problem, but if you can get co-operation working, the EU can be part of the solution to the problem," he said.

Mr Brown said there was a need to "show we can manage globalisation better" and "balance the autonomy that people want with the co-operation we need", adding: "That is what the EU is about."

He said the UK would be "in pole position" to champion change when it takes the rotating presidency of the EU in 2017, if it votes to stay in the EU.

Analysis

By Laura Kuenssberg, BBC political editor

It might pain me to say it, but plenty of political interventions that we report on go unnoticed.

That's why this afternoon, talking to interested members of the public - not all Labour voters but interested parties nonetheless - who had turned up to hear the former PM Gordon Brown speak, it was striking that unprompted many of them mentioned they thought he might "do a Scotland".

Read more from Laura

Mr Brown said Labour's agenda for Remain was a "positive" one, that showed "the benefits that will come from staying part of the European Union".

"It shows that the Labour Party can work at great strength when we all work together," he added.

Ahead of his speech, he told BBC Radio 4's Today: "The Labour voters that I talk to don't like the status quo... They want to know that they are going to be better off, and that's the message I can put."

He also defended current levels of immigration, and said fears over the impact on local communities would be better addressed by increasing investment in stretched public services than ending free movement rights.

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A study by think tank Migration Watch, that wants lower immigration, has forecast net migration would run at more than a quarter of a million a year for at least 20 years if Britain stayed in the EU.

Mr Brown insisted "illegal immigration" was the biggest problem the UK faced, and said the only way to tackle it was from within the EU, with cross-border co-operation.

Ex-Tory cabinet minister and Vote Leave campaigner Iain Duncan Smith said Labour was "lecturing" rather than listening to its own supporters over immigration.

Traditional Labour voters were "pretty disgusted" with the party over its pro-EU stance, he said and added: "The number one thing they want is migration brought under control and Labour has nothing to say on that matter."

Image copyright Getty Images Image caption Hilary Benn (left) said migrants were crucial for the economy

At a separate event on Monday, shadow foreign secretary Hilary Benn acknowledged there was widespread unease among many traditional Labour communities about the impact of immigration.

But he warned: "The truth is that leaving the EU is not going to stop immigration."

Labour MP and Vote Leave chairwoman Gisela Stuart said her party's voters "have now seen through government spin and no amount of hastily cobbled together re-launches" would change that.

"We know that hardworking British people are feeling the strains caused by uncontrolled migration - and that they are sick and tired of being told their concerns are somehow illegitimate.

"The Remain campaign have nothing to say on immigration, and Gordon Brown added nothing to their case today."