Former Labour leader Ed Miliband has joined forces with Jeremy Corbyn for the first since his successor took over the party as the pair campaign against Brexit together.
Despite talk about tension between the two politicians, they put on a united front at a Remain rally of grass roots Labour supporters in the north of England to show "solidarity" with the European Union..
At a rally in Doncaster, where Mr Miliband is an MP, the former leader urged Labour voters to think of the message that Brexit would send to the rest of Europe and uphold historic links with the continent.
Mr Miliband said young people "take for granted the ability to travel across borders, to work elsewhere, to study elsewhere - think of their future, put their future first".
The pair visited Raventhorpe solar farm in north Lincolnshire to deliver a message that Brexit will hinder the fight against climate change because the EU gives Britain clout at global negotiations, and helps fund the development of green technologies.
Mr Corbyn said leaving the EU would pose a threat to fresh air quality and clean beaches.
"Leaving the EU would mean the green spaces, clean beaches and fresh air we want to leave for our children could be at risk," he said.
"It would risk investment in new green technologies and the jobs that accompany them, and would leave us open to the Tory agenda, which has been so damaging to our environment."
Mr Miliband, who led Labour during the party's disastrous result at the last general election, said voters have a duty to consider the environment.
"The challenge of tackling climate change is a moral responsibility, an economic necessity and the single most important thing we can do for our children and our grandchildren, and leaving the EU would rob us of the ability to overcome that challenge," he said.