Latest results announced today show statutory pre-tax losses increased from £17.4m last time on annual turnover down to £335.8m from £342.4m.
HSS said it was hit by exceptional costs of £66.6m as it continues a cost cutting programme and strategic review of the business.
Chief Executive Officer Steve Ashmore said: “Overall 2017 was a difficult year for HSS, mainly due to the impact of operational changes made in 2016.
“We have addressed this by focusing on the core rental business and reducing our cost base and I am pleased with how the business responded in the second half of the year.
“When I arrived in June, I instigated a thorough strategic review process, the results of which have given us clear direction and an ambition to restore the business to historic levels of performance.
“Whilst we are only a few months into implementing the strategy, early signs are encouraging, and we are pleased with the results of the changes made to our network and the associated cost savings.”
During the year the number of staff employed by HSS reduced from 3,254 to 3,006 and spending on new equipment fell to £25.7m from £27.3m.