Warning from an unlikely source: As Burnham's sovereignty surrender begins today - Cameron tells the PM not to rejoin the EU

David Cameron last night warned Andy Burnham not to take Britain back into the EU.

As the Prime Minister prepares to sell his Brexit betrayal to European leaders today, his predecessor, an arch-Remainer, cautioned against triggering another 'decade-long debate about whether we should be in or out'.

Mr Burnham will travel to Dublin for a gathering of Emmanuel Macron's 'EU-lite' – the European Political Community – where he will 'sound out' other leaders on the price of Britain realigning with Brussels. 

But ahead of the trip, Lord Cameron warned the Prime Minister not to make the same mistakes he did. 

Britain should not enter a customs union with the EU, the former Tory leader said, while even starting a conversation about rejoining would be 'very long and painful'.

Mr Burnham will today lay the groundwork for a major UK-EU summit in Brussels next week.

He is said to hope that, by signalling a willingness to rejoin the bloc, he can secure a last-minute deal to align Britain with a series of EU rules ahead of next Friday's summit.

Mr Burnham will hold bilateral meetings with EU leaders today and Downing Street said he would use the Dublin gathering of the European Political Community – a forum for political and strategic discussions about the future of Europe, introduced by French president Macron – to 'drive forward his agenda' on forging a new relationship.

David Cameron last night warned Andy Burnham not to take Britain back into the EU

Mr Burnham will today lay the groundwork for a major UK-EU summit in Brussels next week

A Whitehall source said the Prime Minister had still not met the leaders of many EU member states and would use the event to 'sound them out' on the options for the future.

Mr Burnham has said he plans to use the UK-EU summit to launch a 'conversation' on Britain's future with Brussels, with options including fully rejoining the bloc.

But last night Lord Cameron, who stood down as PM having lost the 2016 Brexit referendum, said: 'Instead of launching an argument about rejoining – which I think would be a very long and painful argument, and who knows where it would end up – focus on how do we be the best friend, best neighbour, best partner.'

He also warned that by 'flirting with rejoining' the EU, Mr Burnham will weaken Britain's position in any future negotiations with Brussels.

'If you start endlessly producing this idea that we're actually on a path to rejoining, I think you're in danger of getting a less good partnership deal because of course the EU countries will just think, "Well, these guys are going to rejoin anyway, so what's the point in giving them a good partnership deal?"' he told Bloomberg.

'If you're not going to commit to trying to make the partnership stronger because you're flirting with rejoining, I think there's some dangers there.'

Lord Cameron also said that Britain's problems of 'overspending, over-borrowing, over-taxing' and the spiralling cost of welfare 'have nothing to do with Brexit'.

He added: 'Do we really want to go into another decade-long debate about whether we should be in or out, when actually we should deal with our own problems while making the partnership model work?'

The former prime minister admitted he was 'desperately disappointed that we lost that campaign [to stay in the EU],' but added: 'I'm a democrat, a believer in democracy – we voted to leave.'

His comments come as the Prime Minister struggles to contain a split in Cabinet over Brexit, with ministers this week using a private meeting to air disagreements over the Government's EU strategy.

Former home secretary Dame Priti Patel said: 'Burnham is delusional if he thinks that rejoining the EU and having closer ties with Brussels at any cost to taxpayers will be a game-changer for economic growth and tackling illegal migration'

There was a 'clear divide between those who want to go further and those who don't want to push the issue too far,' according to The i Paper.

And last night Brexiteers rounded on the PM for his 'delusional' attempts to get closer to Europe.

Former home secretary Dame Priti Patel said: 'Burnham is delusional if he thinks that rejoining the EU and having closer ties with Brussels at any cost to taxpayers will be a game-changer for economic growth and tackling illegal migration. 

'He and his out-of-touch ministers should scrap their tax-grabbing, business-bashing, job-destroying policies and start delivering for the British people rather than plotting to rejoin a failed EU Club.'

Speaking in the Commons yesterday, Mr Burnham said he did not want to rejoin the single market 'today' – but did not rule out doing so in the future.

The PM said he would stick to Labour's 'red lines' on Brexit until the next election, ruling out an immediate move to rejoin.

But he said a food and farming deal with the EU could add 0.4 per cent to the UK's GDP over time and was 'worth taking'.

• QUENTIN LETTS: Burnham's so passive, indecisive, bland. No wonder he's got Boston Consulting to write his Ten-Year Plan 
• DAN HODGES: Ten-year plan? The PM barely has a ten-week plan. Everyone in No10 can see that he doesn't know what he's doing 
• READ MORE: 'There is no grand plan. It's just spin': Ministers hit out as PM says his blueprint for UK will be out in weeks  
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• DAILY MAIL COMMENT: Wise words for PM...