The Bootle-headquartered business reported a turnover of £7.6m for the year to 30 September 2013, up from £6.9m in the previous year.
ISP, which was founded in 1981, said pre-tax profits in the trading company alone rose by 80 per cent to more than £600,000. Staff numbers are also up from 98 employees to 115.
Managing director John Rogers said: "We have enjoyed a terrific year at ISP with greater demand than ever before for our products. Our core business has again been in the manufacture and supply of lifejackets to a broad mix of sectors including military and defence, commercial and leisure.
"ISP is a truly global manufacturing business with exports accounting for more than 65 per cent of sales. The military sector has featured very heavily again in overall sales."
Rogers added ISP has enjoyed strong business with the UK Ministry of Defence and continued to develop its overseas profile with particular success in Australia, New Zealand, Singapore and Malaysia.
"Sales are way up on the first quarter of last year and we are currently enjoying one of our busiest months of trade. This should stimulate further employment opportunities and business growth," said Rogers.