The sweet summer morning sight of birds pecking the top of milk bottles could be causing food poisoning for scores of families.

Environmental health officers are warning that drinking milk when the foil caps have been pecked by birds can cause campylobacter food poisoning.

Since May 1, a total of 67 cases have been reported to Calderdale Council, ten of which have been put down to drinking bird-pecked milk. Since January 1, there have been 162 incidents of campylobacter, as opposed to 12 of salmonella.

In Bradford there were 626 cases reported last year, up 15 from the previous year. Levels reached their peak in 1996 when there were 880 incidents in the district.

The risk of contracting the bug rises during the summer and people are being warned to take care not to fall foul of the virus which can cause severe diarrhoea, fever and intense abdominal pain.

Campylobacter can be found in the intestines of wild or domestic birds, animals, cattle and domestic pets.

Usually the infection takes up to five days to show itself and only a small amount of bacteria is enough to cause an illness.