The G7 warning was included in a 32-page declaration, in the section that talks about non-economic threats, and also includes concerns over geopolitical conflicts, terrorism and the refugee crisis.
It said: “A UK exit from the EU would reverse the trend towards greater global trade and investment, and the jobs they create and is a further serious risk to growth.”
The wording appears to have been added at the 11th hour, because it was not included in the section on the #global economy in a draft on Thursday night.
Other leaders also revealed that Brexit was not discussed in a series of sessions that covered the economy, trade, counter-terrorism and sanctions on Russia.
The British prime minister, David Cameron, is likely to highlight the words, that come just hours after purdah rules in the UK prevent the civil service from issuing any further reports about the potential risks to jobs, pensions or mortgages.