Carillion has stepped up security around its Manchester office after a demonstration against a detention centre at Manchester airport by an immigrants’ rights group.

The contractor has increased patrols round its perimeter fence and car park from four times a day to every half hour.

The protest was staged by Manchester No Borders, part of a group opposed to immigration controls, to draw attention to the firm’s involvement in the extension of a short-term holding facility. The protest was broken up by the police after 10 minutes.

Carillion confirmed it was in talks with Group 4 Securicor, the detention centre’s operator, but said it had not yet prequalified as contractor on the project.

Meanwhile, Carillion this week reported a 23% jump in profit off the back of a healthy support services market and stronger than expected savings from its Mowlem acquisition.

In its results for 2007 it reported an underlying pre-tax profit of £101.8m, up from £82.6m in 2006. Turnover rose 13% to £3.95bn, up from £3.51bn. Construction margins grew to 2.1% from 1.7%.