The chain was identified by the Home Office, which came under attack from the official statistics watchdog for the way it had issued figures showing a fall in violent crime since the relaxation of licensing laws.

Findings from an alcohol enforcement campaign suggested that Waitrose had the worst record for selling alcohol to under-18s, followed by Somerfield and the Co-op.

Waitrose sold alcohol in 22 per cent of cases where trading standards officers used under-18s in secret test purchases. The other big chains similarly tested were Somerfield (20 per cent) the Co-op (17 per cent), Tesco and Sainsbury (both 16 per cent) and Morrisons (15 per cent).

Christian Cull, the marketing director of Waitrose, said: “The sample was small, but it does show that there is clear room for improvement.

“I can assure our customers that my colleagues in all our shops take great pride in the levels of service they provide. They also take the matter of under-age sales very seriously.”

Separate figures released by the Home Office on violent crime in December stirred up controversy over its use of crime figures only weeks after the Statistics Commission had said that public trust had been undermined by the way it released figures.

A Home Office statement issued yesterday said that violent crime, including murder, rape, robbery and violent attacks on the street, fell by 11 per cent, including a 21 per cent fall in serious violent crime. No details on the statistical basis of the fall were in the statement.

Initially the Home Office said that the falls were a comparison of violent crime recorded by police in England and Wales in October with the total figures for November and December. A spokesman later said that the 11 per cent fall was a comparison of all violent crime in October with all violent crime in December. The department usually releases figures on a quarterly basis.

Police chiefs, opposition politicans and the Statistics Commission criticised the way the the figures were released.

Richard Alldritt, chief executive of the Statistics Commission said: “We would like to see a proper statistical statement.”

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