Britain’s exit from the European Union has reduced the size of the economy by 6 percent so far — an annual cost of 140 billion pounds ($178 billion) — London Mayor Sadiq Khan said today, with the impact on the economy expected to reach 10 percent by 2035.

Khan, a member of the opposition Labor Party, which voted against Brexit in the 2016 referendum, based the statement on a report commissioned by Cambridge Econometrics, which calculated how fast the economy would grow if the British were in favor of remaining in the EU.

“It is now clear that Brexit is not working. The hard Brexit we ended up with is dragging our economy down and driving up the cost of living,” Khan said in comments released ahead of a speech he is expected to deliver later today.

Labor has a big lead over the prime minister’s Conservatives Rishi Sunak ahead of the elections, which Sunak plans to call in the second half of this year.

But Labor leader Keir Starmer has appeared reticent to give details of how he plans to strengthen relations with the EU.

Cambridge Econometrics’ estimate of the cost of Brexit is higher than other recent estimates.

The British National Institute for Economic and Social Research (NIESR) estimated in November that Brexit has reduced the size of the economy by 2-3%, with the impact expected to increase to 5%-6% by 2035.

Jonathan Haskell, a policy-making official at the Bank of England, estimated last year, expressing his own views, that Brexit had badly damaged business investment by reducing GDP by 1.3% by the end of 2022 – the equivalent of 1,000 pounds per household per year.

Cambridge Econometrics said Brexit was expected to slow annual economic growth in Britain by 0.4 of a percentage point between now and 2035 and reduce investment by a third.

Assessing the impact of Brexit has been complicated by the COVID-19 pandemic just months after Britain officially left the EU in January 2020.

Net migration to Britain has jumped as a new work visa system led to a large increase in migration to Britain from outside the EU, offsetting a decline in the number of EU migrants who previously did not need a visa.