Lawyers acting for an immigrants’ welfare group are to challenge the legality of the government’s temporary cap on immigration.

The Joint Council for the Welfare of Immigrants (JCWI) has sent a pre-action protocol letter to the Home Office, informing it of its intention to launch judicial review proceedings seeking to overturn the cap.

In June, the government put a temporary cap on the number of skilled migrants from outside Europe who will be admitted to the UK, to prevent a surge in applications before a permanent cap comes into force in April 2011.

The JCWI claims the temporary cap is unlawful, because the home secretary imposed it without parliamentary approval.

The challenge has been welcomed by lawyers concerned by the impact of the cap on the legal sector.

Sophie Barrett-Brown, chair of the Immigration Lawyers Practitioners Association, said: ‘Many law firms, including this one, have been adversely affected by the temporary cap. We were refused a licence to bring a US lawyer to London, while other firms have been unable to renew contracts for non-EU lawyers already working here. The cap has no commercial basis.’

Immigration minister Damian Green said the Home Office would ‘rigorously defend’ the challenge and was ‘confident of success’.

The Law Society made a submission to the Home Office last month, warning that the immigration restrictions could damage the legal sector.