If Britain fails to agree on a trade deal with the European Union, the UK could lose half a million jobs and almost £50 billion in investment by 2030 – according to a report commissioned by Sadiq Khan.

The economic forecast is based on five different Brexit scenarios, the worst of which is a “no-deal” exit that would lead to “lost decade” of an economic slump.

“If the government continue to mishandle the negotiations we could be heading for a lost decade of lower growth and lower employment,” said Khan. “The analysis concludes that the harder the Brexit we end up with, the bigger the potential impact on jobs, growth and living standards.”

The report concludes that “the harder the Brexit, the more severe the economic damage could be”. Khan was an adamant remainer throughout the Brexit campaign.

The analysis by Cambridge Econometrics still predicts that a soft Brexit will still lead to 176,000 fewer jobs by 2030 and a loss of £20 billion in investment.

“London does least worst, because we have a higher concentration of high-value jobs, we are more resilient, more able to recover from economic shock, which could lead to the inequalities between London and the country getting worse …” he said on BBC Radio 4’s Today programme.

“Whatever scenario we look at when it comes to leaving the EU, the inequalities between London and the south-east and the country widen, not narrow.”

“I’ve released these impact assessments because the British people and our businesses have a right to know the likely impact of the various options the government are considering on their lives and personal finances.

“This new analysis shows why the government should now change its approach and negotiate a deal that enables us to remain in both the single market and the customs union.”