Britain's divorce from the European Union is costing the economy about £600m per week since the 2016 referendum, Goldman Sachs said in a report that underscores how Brexit uncertainty has dented investment.
The report found that Brexit had cost the world's fifth largest economy nearly 2.5% of GDP at the end of last year, compared to its growth path prior to the mid-2016 vote on exiting the bloc.
It argues that had UK voters opted to remain, the economy would have been in a much stronger position, instead of underperforming and lagging behind other advanced economies.
Goldman's analysis comes after government plans to exit the EU have been repeatedly knocked back by parliament, increasing the uncertainty over the path of Brexit with the original divorce date of March 29 now pushed back to mid-April.
The resulting uncertainty over the future political and economic relationship with the EU has had real costs for the UK economy, which have spilled over to other economies"
"Politicians in the UK are still struggling to deliver on that vote," Goldman Sachs economists wrote in a note to clients.
"The resulting uncertainty over the future political and economic relationship with the EU has had real costs for the UK economy, which have spilled over to other economies."
The US bank said Brexit uncertainty has been a major driver of economic output losses as they are concentrated in investment.
"Uncertainty shocks weighed on investment growth in the immediate aftermath of the Brexit vote, as well as more recently amid the renewed intensification of Brexit uncertainty," the economists said.
The bank's estimates came as data showed factories in Britain stockpiled for Brexit at an explosive rate last month, unlike anything seen before in a major rich economy and a prelude to a likely sharp investment shortfall ahead.
The report follows a Bank of England analysis that suggested around £40bn per year, or £800m per week, of lost income for the country as a whole since the result of the leave vote.
Goldman added that under a no-deal scenario, favoured by the most extreme Tory Brexiters, the UK will be a big loser, but its European neighbours would also suffer.
It said: "Under our ‘no-deal' scenario, the UK suffers large output losses, in conjunction with a substantial global confidence shock marked by a sharp sterling depreciation. European countries would be most exposed to this scenario and could see output losses of around 1% of real GDP."
Conversely, a "status quo" Brexit transition deal would reverse part of the UK's output underperformance and, under a remain scenario, the UK "fully recoups Brexit-related output costs and business confidence rebounds".