The 12% increase in income to £22 million was attributed to new contracts and retention of existing clients.

Accounts filed at Companies House show pre-tax profit went from £328,816 to £550,123 in 2011.

The directors were "satisfied" with the performance but warned price pressures had affected margins.

In notes to the accounts they added: "The current trading conditions will continue for 2012 and probably beyond.

"We are targeting new market segments in the current year in order to continue our recent business growth.

"This combined with our focus on service delivery to existing clients and tight cost controls should result in a positive outcome for the current year."

Directors' emoluments in 2011 increased from £364,338 to £370,364 with the highest paid seeing their remuneration rise from £132,512 to £135,938.