To ask Her Majesty's Government what estimate they have made of the number of rats in the United Kingdom in each year for which figures are available since 2001. [HL3801]

To ask Her Majesty's Government what assessment they have made of reports that rats have developed an immunity to standard poisons; and what plans they have to counter any increase in the rat population. [HL3802]

The Government do not hold data on the size of the UK rat population. However, the latest report on rodent presence in domestic properties as revealed by the English House Condition Survey data for 2002-03 and 2003-04 is available on Defra's website. Key findings are that the occurrences of rats inside and outside properties in these years are not significantly different from those observed in 2001.

The former Ministry of Agriculture, Fisheries and Food funded an assessment of resistance to rodenticides in 1998. This was published in: Kerins, G.M.; Dennis, N.; Atterby, H.; Gill, J.E. & MacNicoll A.D. (2001) Distribution of resistance to anticoagulant rodenticides in the Norway rat (Rattus norvegicus Berk.) in England 1995-98. In: Advances in Vertebrate Pest Management Volume II (Eds. H-J Pelz, D.P Cowan & C.J. Feare) pages 149-159, Filander Verlag, Furth.

The Health and Safety Executive is aware from literature that rats may be becoming increasingly resistant to anticoagulant rodenticides. Although it is aware of the research mentioned above, it is not aware of any new studies and has not itself commissioned any recent work of this nature. The department is currently considering whether it is possible to allow more effective rodenticide to be deployed.

Under the Prevention of Damage by Pests Act 1949, local authorities have a duty to take such steps as may be necessary to secure, so far as is practicable, that their districts are kept free from rats and mice.