SIR - Mr Pashley is correct to challenge the spurious arguments often given to justify immigration (Letters, December 12).

A small number of people entering the country can be accommodated within the existing system, provided a sustainable population is maintained. Although Northern Ireland, Scotland and Wales are lightly populated, England is now one of the most densely populated regions in Europe, and further net migration will only worsen an already unsustainable situation as regards demands on services and infrastructure.

It has been estimated that based on our landmass for providing most of our own food, a sustainable population for the UK is between 25-30 million.

At one level it would be expected that the Green party would campaign for a sustainable population, but would regard constraints on immigration as infringing the human rights of migrants, thus contradicting its own rhetoric.

Of the political parties contesting the forthcoming General Election, only Ukip could be trusted to take the necessary action to control net migration, but would have to hold the balance of power to be able to implement its policies.

Alec Suchi, Allerton Road, Bradford