Former prime minister David Cameron has warned Andy Burnham against reopening the debate on rejoining the European Union, saying it would be a very long and painful argument that could leave Britain with a worse deal from Brussels.

Speaking to Bloomberg on Wednesday, Lord Cameron said the UK should focus instead on being the EU's best friend, best neighbour and best partner, rather than starting a fresh argument about membership.

He 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, instead of that, focus on how do we be the best friend, best neighbour, best partner."

Warning over a weaker partnership deal

Lord Cameron warned that constantly suggesting Britain is on a path back into the EU could undermine negotiations over a closer partnership. He said EU countries would see little point in offering a good partnership deal if they believed the UK would rejoin anyway.

"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," he said.

He added that if Britain did not commit to strengthening the partnership because it was "flirting with rejoining", there were dangers in that approach.

Brexit not to blame for economic problems

The former Conservative leader, who led the Remain campaign in the 2016 referendum, said Britain's economic problems were not caused by Brexit. He pointed instead to overspending, over-borrowing, over-taxing, over-regulation and high spending on working-age welfare.

"None of those have got anything to do with Europe," he said, arguing that the government should deal with its own problems while making the partnership model work, rather than going into another decade-long debate about whether Britain should be in or out.

Lord Cameron said rejoining the EU would not solve the UK's problems and could be a barrier to fixing them. He also said he would not favour further integration such as rejoining the customs union.

Summit ahead in Brussels

The intervention comes days before a UK-EU summit in Brussels on 20 November. Mr Burnham has made closer ties with the EU a key priority of his premiership and is preparing to set out options for Britain's future relationship with the bloc in a speech in the coming weeks.

The prime minister is due to sign a new deal with Brussels next week under which the UK will follow European food standards rules in return for an end to checks in the Channel and the Irish Sea.

Lord Cameron said he had fought the campaign to stay in the EU on an amended basis and was desperately disappointed to lose, but added: "I'm a democrat, a believer in democracy."