Sir Paul McCartney called on people to consider altering their eating habits to "strike a blow for the environment, our children and the future".
He drew attention to a United Nations report which found that the livestock sector generates more greenhouse gas emissions as measured in CO2 equivalent - 18% - than transport.
In a letter to the Press Association he quoted Henning Steinfeld, chief of the UN Food and Agriculture Organisation's livestock information and policy branch, who said: "Livestock are one of the most significant contributors to today's most serious environmental problems. Urgent action is required to remedy the situation."
Sir Paul said the report, Livestock's Long Shadow - Environmental Issues And Options, contained one clear message - that the single most effective act that any individual can currently do to lessen the effects of global warming is to become vegetarian.
"That this message comes directly from an authoritative body such as the UN (whose member states, it should be remembered, are not generally considered vegetarian) rather than an organisation committed to vegetarianism is significant."